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Posted to commits@commons.apache.org by gg...@apache.org on 2024/09/30 17:12:56 UTC

(commons-text) branch master updated: Make test more readable and maintainable, and less verbose

This is an automated email from the ASF dual-hosted git repository.

ggregory pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-text.git


The following commit(s) were added to refs/heads/master by this push:
     new 2c43b010 Make test more readable and maintainable, and less verbose
2c43b010 is described below

commit 2c43b01016f5218b2cd79b053e8ffaba01a31c5a
Author: Gary Gregory <ga...@gmail.com>
AuthorDate: Mon Sep 30 13:12:49 2024 -0400

    Make test more readable and maintainable, and less verbose
    
    - Use JUnit 5 APIs
    - Be consistent throughout tests
---
 pom.xml                                            |   6 -
 .../apache/commons/text/AlphabetConverterTest.java | 157 +++---
 .../org/apache/commons/text/CaseUtilsTest.java     |  70 +--
 .../commons/text/CharacterPredicatesTest.java      | 113 ++--
 .../commons/text/ExtendedMessageFormatTest.java    | 154 +++---
 .../apache/commons/text/FormattableUtilsTest.java  | 140 +++--
 .../java/org/apache/commons/text/OssFuzzTest.java  | Bin 16930 -> 16930 bytes
 .../commons/text/RandomStringGeneratorTest.java    |  79 ++-
 .../commons/text/StrBuilderAppendInsertTest.java   | 578 +++++++++++----------
 .../org/apache/commons/text/StrBuilderTest.java    | 113 ++--
 .../org/apache/commons/text/StrMatcherTest.java    | 182 +++----
 .../apache/commons/text/StrSubstitutorTest.java    |   3 +-
 .../apache/commons/text/StringSubstitutorTest.java | 135 ++---
 .../text/TextStringBuilderAppendInsertTest.java    | 448 ++++++++--------
 .../apache/commons/text/TextStringBuilderTest.java |  50 +-
 .../org/apache/commons/text/WordUtilsTest.java     | 572 ++++++++++----------
 .../commons/text/diff/ReplacementsFinderTest.java  |   4 +-
 .../commons/text/diff/StringsComparatorTest.java   |   9 +-
 .../text/matcher/StringMatcherOnCharArrayTest.java | 376 +++++++-------
 .../StringMatcherOnCharSequenceStringTest.java     | 374 +++++++------
 .../text/similarity/CosineDistanceTest.java        |  13 +-
 .../text/similarity/CosineSimilarityTest.java      |  19 +-
 .../commons/text/similarity/FuzzyScoreTest.java    |  30 +-
 .../text/similarity/HammingDistanceTest.java       |  20 +-
 .../similarity/IntersectionSimilarityTest.java     |  23 +-
 .../text/similarity/JaccardDistanceTest.java       |   8 +-
 .../text/similarity/JaccardSimilarityTest.java     |   8 +-
 .../text/similarity/LevenshteinDistanceTest.java   |   8 +-
 .../text/similarity/LevenshteinResultsTest.java    |  24 +-
 .../LongestCommonSubsequenceDistanceTest.java      |  36 +-
 .../similarity/LongestCommonSubsequenceTest.java   | 104 ++--
 .../ParameterizedEditDistanceFromTest.java         |   7 +-
 .../ParameterizedLevenshteinDistanceTest.java      |  10 +-
 .../ParameterizedSimilarityScoreFromTest.java      |  20 +-
 .../text/similarity/SimilarityScoreFromTest.java   |  12 +-
 .../text/similarity/StringMetricFromTest.java      |  19 +-
 .../text/translate/AggregateTranslatorTest.java    |  14 +-
 .../text/translate/CodePointTranslatorTest.java    |   4 +-
 .../commons/text/translate/CsvTranslatorsTest.java |  22 +-
 .../commons/text/translate/EntityArraysTest.java   |  16 +-
 .../text/translate/JavaUnicodeEscaperTest.java     |  16 +-
 .../text/translate/LookupTranslatorTest.java       |  16 +-
 .../text/translate/NumericEntityEscaperTest.java   |  12 +-
 .../text/translate/NumericEntityUnescaperTest.java |  24 +-
 .../commons/text/translate/OctalUnescaperTest.java |  29 +-
 .../text/translate/SinglePassTranslatorTest.java   |  14 +-
 .../commons/text/translate/UnicodeEscaperTest.java |  28 +-
 .../text/translate/UnicodeUnescaperTest.java       |  19 +-
 .../UnicodeUnpairedSurrogateRemoverTest.java       |  16 +-
 49 files changed, 2002 insertions(+), 2152 deletions(-)

diff --git a/pom.xml b/pom.xml
index 8cd88d77..419d3761 100644
--- a/pom.xml
+++ b/pom.xml
@@ -106,12 +106,6 @@
       <version>${commons.bytebuddy.version}</version>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>org.assertj</groupId>
-      <artifactId>assertj-core</artifactId>
-      <version>3.26.3</version>
-      <scope>test</scope>
-    </dependency>
     <dependency>
       <groupId>commons-io</groupId>
       <artifactId>commons-io</artifactId>
diff --git a/src/test/java/org/apache/commons/text/AlphabetConverterTest.java b/src/test/java/org/apache/commons/text/AlphabetConverterTest.java
index b17fad88..59e78372 100644
--- a/src/test/java/org/apache/commons/text/AlphabetConverterTest.java
+++ b/src/test/java/org/apache/commons/text/AlphabetConverterTest.java
@@ -16,9 +16,11 @@
  */
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.UnsupportedEncodingException;
 import java.util.Arrays;
@@ -34,52 +36,52 @@ import org.junit.jupiter.api.Test;
  */
 public class AlphabetConverterTest {
 
-    private static final Character[] LOWER_CASE_ENGLISH = {' ', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
-        't', 'u', 'v', 'w', 'x', 'y', 'z'};
+    private static final Character[] LOWER_CASE_ENGLISH = { ' ', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
+            't', 'u', 'v', 'w', 'x', 'y', 'z' };
 
-    private static final Character[] ENGLISH_AND_NUMBERS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
-        'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
-        'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', ' '};
+    private static final Character[] ENGLISH_AND_NUMBERS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
+            'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
+            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', ' ' };
 
-    private static final Character[] LOWER_CASE_ENGLISH_AND_NUMBERS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h',
-        'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', ' '};
+    private static final Character[] LOWER_CASE_ENGLISH_AND_NUMBERS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
+            'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', ' ' };
 
-    private static final Character[] NUMBERS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
+    private static final Character[] NUMBERS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
 
-    private static final Character[] BINARY = {'0', '1'};
+    private static final Character[] BINARY = { '0', '1' };
 
-    private static final Character[] HEBREW = {'_', ' ', '\u05e7', '\u05e8', '\u05d0', '\u05d8', '\u05d5', '\u05df', '\u05dd', '\u05e4', '\u05e9', '\u05d3',
-        '\u05d2', '\u05db', '\u05e2', '\u05d9', '\u05d7', '\u05dc', '\u05da', '\u05e3', '\u05d6', '\u05e1', '\u05d1', '\u05d4', '\u05e0', '\u05de', '\u05e6',
-        '\u05ea', '\u05e5'};
+    private static final Character[] HEBREW = { '_', ' ', '\u05e7', '\u05e8', '\u05d0', '\u05d8', '\u05d5', '\u05df', '\u05dd', '\u05e4', '\u05e9', '\u05d3',
+            '\u05d2', '\u05db', '\u05e2', '\u05d9', '\u05d7', '\u05dc', '\u05da', '\u05e3', '\u05d6', '\u05e1', '\u05d1', '\u05d4', '\u05e0', '\u05de',
+            '\u05e6', '\u05ea', '\u05e5' };
 
-    private static final Integer[] UNICODE = {32, 35395, 35397, 36302, 36291, 35203, 35201, 35215, 35219, 35268, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106,
-        107, 108, 109, 110, 1001, 1002, 1003, 1004, 1005};
+    private static final Integer[] UNICODE = { 32, 35395, 35397, 36302, 36291, 35203, 35201, 35215, 35219, 35268, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106,
+            107, 108, 109, 110, 1001, 1002, 1003, 1004, 1005 };
 
-    private static final Integer[] LOWER_CASE_ENGLISH_CODEPOINTS = {32, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114,
-        115, 116, 117, 118, 119, 120, 121, 122};
+    private static final Integer[] LOWER_CASE_ENGLISH_CODEPOINTS = { 32, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114,
+            115, 116, 117, 118, 119, 120, 121, 122 };
 
-    private static final Integer[] DO_NOT_ENCODE_CODEPOINTS = {32, 97, 98, 99}; // space, a, b, c
+    private static final Integer[] DO_NOT_ENCODE_CODEPOINTS = { 32, 97, 98, 99 }; // space, a, b, c
 
     private AlphabetConverter createJavadocExample() {
-        final Character[] original = {'a', 'b', 'c', 'd'};
-        final Character[] encoding = {'0', '1', 'd'};
-        final Character[] doNotEncode = {'d'};
+        final Character[] original = { 'a', 'b', 'c', 'd' };
+        final Character[] encoding = { '0', '1', 'd' };
+        final Character[] doNotEncode = { 'd' };
 
         return AlphabetConverter.createConverterFromChars(original, encoding, doNotEncode);
     }
 
     private void test(final Character[] originalChars, final Character[] encodingChars, final Character[] doNotEncodeChars, final String... strings)
-        throws UnsupportedEncodingException {
+            throws UnsupportedEncodingException {
 
         final AlphabetConverter ac = AlphabetConverter.createConverterFromChars(originalChars, encodingChars, doNotEncodeChars);
 
         final AlphabetConverter reconstructedAlphabetConverter = AlphabetConverter.createConverterFromMap(ac.getOriginalToEncoded());
 
-        assertThat(reconstructedAlphabetConverter).isEqualTo(ac);
-        assertThat(reconstructedAlphabetConverter.hashCode()).isEqualTo(ac.hashCode());
-        assertThat(reconstructedAlphabetConverter.toString()).isEqualTo(ac.toString());
-        assertThat(ac.encode(null)).isNull(); // test null conversions
-        assertThat(ac.encode("")).isEqualTo(""); // test empty conversion
+        assertEquals(ac, reconstructedAlphabetConverter);
+        assertEquals(ac.hashCode(), reconstructedAlphabetConverter.hashCode());
+        assertEquals(ac.toString(), reconstructedAlphabetConverter.toString());
+        assertNull(ac.encode(null)); // test null conversions
+        assertEquals("", ac.encode("")); // test empty conversion
 
         // test all the trial strings
         for (final String s : strings) {
@@ -88,7 +90,7 @@ public class AlphabetConverterTest {
             // test that only encoding chars are used
             final List<Character> originalEncodingChars = Arrays.asList(encodingChars);
             for (int i = 0; i < encoded.length(); i++) {
-                assertThat(originalEncodingChars.contains(encoded.charAt(i))).isTrue();
+                assertTrue(originalEncodingChars.contains(encoded.charAt(i)));
             }
 
             final String decoded = ac.decode(encoded);
@@ -96,10 +98,10 @@ public class AlphabetConverterTest {
             // test that only the original alphabet is used after decoding
             final List<Character> originalCharsList = Arrays.asList(originalChars);
             for (int i = 0; i < decoded.length(); i++) {
-                assertThat(originalCharsList.contains(decoded.charAt(i))).isTrue();
+                assertTrue(originalCharsList.contains(decoded.charAt(i)));
             }
 
-            assertThat(decoded).as("Encoded '" + s + "' into '" + encoded + "', but decoded into '" + decoded + "'").isEqualTo(s);
+            assertEquals(s, decoded, () -> "Encoded '" + s + "' into '" + encoded + "', but decoded into '" + decoded + "'");
         }
     }
 
@@ -119,7 +121,7 @@ public class AlphabetConverterTest {
         characterArray[1] = characterArray[0];
         final AlphabetConverter alphabetConverter = AlphabetConverter.createConverterFromChars(characterArray, characterArray, characterArray);
 
-        assertThat(alphabetConverter.equals(charOne)).isFalse();
+        assertFalse(alphabetConverter.equals(charOne));
     }
 
     @Test
@@ -129,16 +131,15 @@ public class AlphabetConverterTest {
         characterArray[1] = characterArray[0];
         final AlphabetConverter alphabetConverter = AlphabetConverter.createConverterFromChars(characterArray, characterArray, characterArray);
 
-        assertThat(alphabetConverter.getEncodedCharLength()).isEqualTo(1);
+        assertEquals(1, alphabetConverter.getEncodedCharLength());
     }
 
     @Test
     public void testCreateConverterFromCharsWithNullAndNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> {
+        assertThrows(IllegalArgumentException.class, () -> {
             final Character[] characterArray = new Character[2];
             characterArray[0] = '$';
             characterArray[1] = characterArray[0];
-
             AlphabetConverter.createConverterFromChars(characterArray, null, null);
         });
     }
@@ -149,9 +150,8 @@ public class AlphabetConverterTest {
         final AlphabetConverter alphabetConverter = AlphabetConverter.createConverterFromMap(hashMap);
         hashMap.put(0, "CtDs");
         final AlphabetConverter alphabetConverterTwo = AlphabetConverter.createConverterFromMap(hashMap);
-
-        assertThat(alphabetConverter.equals(alphabetConverterTwo)).isFalse();
-        assertThat(alphabetConverter.getEncodedCharLength()).isEqualTo(1);
+        assertFalse(alphabetConverter.equals(alphabetConverterTwo));
+        assertEquals(1, alphabetConverter.getEncodedCharLength());
     }
 
     @Test
@@ -159,8 +159,7 @@ public class AlphabetConverterTest {
         final Map<Integer, String> map = new HashMap<>();
         final AlphabetConverter alphabetConverter = AlphabetConverter.createConverterFromMap(map);
         alphabetConverter.decode(null);
-
-        assertThat(alphabetConverter.getEncodedCharLength()).isEqualTo(1);
+        assertEquals(1, alphabetConverter.getEncodedCharLength());
     }
 
     @Test
@@ -171,8 +170,8 @@ public class AlphabetConverterTest {
 
     @Test
     public void testEncodeFailureTest() {
-        assertThatThrownBy(() -> test(BINARY, NUMBERS, ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY, "3")).isInstanceOf(UnsupportedEncodingException.class)
-            .hasMessage("Couldn't find encoding for '3' in 3");
+        assertEquals("Couldn't find encoding for '3' in 3",
+                assertThrows(UnsupportedEncodingException.class, () -> test(BINARY, NUMBERS, ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY, "3")).getMessage());
     }
 
     @Test
@@ -185,8 +184,8 @@ public class AlphabetConverterTest {
         final Map<Integer, String> map = new HashMap<>();
         final AlphabetConverter alphabetConverterTwo = AlphabetConverter.createConverterFromMap(map);
 
-        assertThat(alphabetConverterTwo.getEncodedCharLength()).isEqualTo(1);
-        assertThat(alphabetConverter.equals(alphabetConverterTwo)).isFalse();
+        assertEquals(1, alphabetConverterTwo.getEncodedCharLength());
+        assertFalse(alphabetConverter.equals(alphabetConverterTwo));
     }
 
     @Test
@@ -194,7 +193,7 @@ public class AlphabetConverterTest {
         final Character[] characterArray = ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY;
         final AlphabetConverter alphabetConverter = AlphabetConverter.createConverterFromChars(characterArray, null, null);
 
-        assertThat(alphabetConverter.equals(null)).isFalse();
+        assertFalse(alphabetConverter.equals(null));
     }
 
     @Test
@@ -205,17 +204,17 @@ public class AlphabetConverterTest {
         characterArray[1] = character;
         final AlphabetConverter alphabetConverter = AlphabetConverter.createConverterFromChars(characterArray, characterArray, characterArray);
 
-        assertThat(alphabetConverter.equals(alphabetConverter)).isTrue();
+        assertTrue(alphabetConverter.equals(alphabetConverter));
     }
 
     @Test
     public void testHebrewTest() throws UnsupportedEncodingException {
         test(HEBREW, BINARY, ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY, "\u05d0", "\u05e2",
-            "\u05d0\u05dc\u05e3_\u05d0\u05d5\u05d4\u05d1\u05dc_\u05d1\u05d9\u05ea_\u05d6\u05d4_\u05d1\u05d9\u05ea_"
-                + "\u05d2\u05d9\u05de\u05dc_\u05d6\u05d4_\u05db\u05de\u05dc_\u05d2\u05d3\u05d5\u05dc");
+                "\u05d0\u05dc\u05e3_\u05d0\u05d5\u05d4\u05d1\u05dc_\u05d1\u05d9\u05ea_\u05d6\u05d4_\u05d1\u05d9\u05ea_"
+              + "\u05d2\u05d9\u05de\u05dc_\u05d6\u05d4_\u05db\u05de\u05dc_\u05d2\u05d3\u05d5\u05dc");
         test(HEBREW, NUMBERS, ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY, "\u05d0", "\u05e2",
-            "\u05d0\u05dc\u05e3_\u05d0\u05d5\u05d4\u05d1\u05dc_\u05d1\u05d9\u05ea_\u05d6\u05d4_\u05d1\u05d9\u05ea_"
-                + "\u05d2\u05d9\u05de\u05dc_\u05d6\u05d4_\u05db\u05de\u05dc_\u05d2\u05d3\u05d5\u05dc");
+                "\u05d0\u05dc\u05e3_\u05d0\u05d5\u05d4\u05d1\u05dc_\u05d1\u05d9\u05ea_\u05d6\u05d4_\u05d1\u05d9\u05ea_"
+              + "\u05d2\u05d9\u05de\u05dc_\u05d6\u05d4_\u05db\u05de\u05dc_\u05d2\u05d3\u05d5\u05dc");
         test(NUMBERS, HEBREW, ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY, "123456789", "1", "5");
         test(LOWER_CASE_ENGLISH, HEBREW, ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY, "this is a test");
     }
@@ -227,58 +226,57 @@ public class AlphabetConverterTest {
     public void testJavadocExampleTest() throws UnsupportedEncodingException {
         final AlphabetConverter ac = createJavadocExample();
 
-        assertThat(ac.encode("a")).isEqualTo("00");
-        assertThat(ac.encode("b")).isEqualTo("01");
-        assertThat(ac.encode("c")).isEqualTo("0d");
-        assertThat(ac.encode("d")).isEqualTo("d");
-        assertThat(ac.encode("abcd")).isEqualTo("00010dd");
+        assertEquals("00", ac.encode("a"));
+        assertEquals("01", ac.encode("b"));
+        assertEquals("0d", ac.encode("c"));
+        assertEquals("d", ac.encode("d"));
+        assertEquals("00010dd", ac.encode("abcd"));
     }
 
     @Test
     public void testMissingDoNotEncodeLettersFromEncodingTest() {
-        assertThatThrownBy(() -> AlphabetConverter.createConverterFromChars(ENGLISH_AND_NUMBERS, LOWER_CASE_ENGLISH, NUMBERS))
-            .isInstanceOf(IllegalArgumentException.class).hasMessage("Can not use 'do not encode' list because encoding alphabet does not contain '0'");
+        assertEquals("Can not use 'do not encode' list because encoding alphabet does not contain '0'",
+                assertThrows(IllegalArgumentException.class, () -> AlphabetConverter.createConverterFromChars(ENGLISH_AND_NUMBERS, LOWER_CASE_ENGLISH, NUMBERS))
+                        .getMessage());
     }
 
     @Test
     public void testMissingDoNotEncodeLettersFromOriginalTest() {
-        assertThatThrownBy(() -> AlphabetConverter.createConverterFromChars(LOWER_CASE_ENGLISH, ENGLISH_AND_NUMBERS, NUMBERS))
-            .isInstanceOf(IllegalArgumentException.class).hasMessage("Can not use 'do not encode' list because original alphabet does not contain '0'");
+        assertEquals("Can not use 'do not encode' list because original alphabet does not contain '0'",
+                assertThrows(IllegalArgumentException.class, () -> AlphabetConverter.createConverterFromChars(LOWER_CASE_ENGLISH, ENGLISH_AND_NUMBERS, NUMBERS))
+                        .getMessage());
     }
 
     @Test
     public void testNoEncodingLettersTest() {
-        assertThatThrownBy(() -> AlphabetConverter.createConverterFromChars(ENGLISH_AND_NUMBERS, NUMBERS, NUMBERS)).isInstanceOf(IllegalArgumentException.class)
-            .hasMessage("Must have at least two encoding characters (excluding those in the 'do not encode' list), but has 0");
+        assertEquals("Must have at least two encoding characters (excluding those in the 'do not encode' list), but has 0",
+                assertThrows(IllegalArgumentException.class, () -> AlphabetConverter.createConverterFromChars(ENGLISH_AND_NUMBERS, NUMBERS, NUMBERS))
+                        .getMessage());
     }
 
     @Test
     public void testOnlyOneEncodingLettersTest() {
-        assertThatThrownBy(() -> {
-            final Character[] numbersPlusUnderscore = Arrays.copyOf(NUMBERS, NUMBERS.length + 1);
-            numbersPlusUnderscore[numbersPlusUnderscore.length - 1] = '_';
+        assertEquals("Must have at least two encoding characters (excluding those in the 'do not encode' list), but has 1",
+                assertThrows(IllegalArgumentException.class, () -> {
+                    final Character[] numbersPlusUnderscore = Arrays.copyOf(NUMBERS, NUMBERS.length + 1);
+                    numbersPlusUnderscore[numbersPlusUnderscore.length - 1] = '_';
 
-            AlphabetConverter.createConverterFromChars(ENGLISH_AND_NUMBERS, numbersPlusUnderscore, NUMBERS);
-        }).isInstanceOf(IllegalArgumentException.class)
-            .hasMessage("Must have at least two encoding characters (excluding those in the 'do not encode' list), but has 1");
+                    AlphabetConverter.createConverterFromChars(ENGLISH_AND_NUMBERS, numbersPlusUnderscore, NUMBERS);
+                }).getMessage());
     }
 
     @Test
     public void testUnexpectedEndWhileDecodingTest() {
         final String toDecode = "00d01d0";
-        assertThatThrownBy(() -> {
-            final AlphabetConverter ac = createJavadocExample();
-            ac.decode(toDecode);
-        }).isInstanceOf(UnsupportedEncodingException.class).hasMessage("Unexpected end of string while decoding " + toDecode);
+        assertEquals("Unexpected end of string while decoding " + toDecode,
+                assertThrows(UnsupportedEncodingException.class, () -> createJavadocExample().decode(toDecode)).getMessage());
     }
 
     @Test
     public void testUnexpectedStringWhileDecodingTest() {
         final String toDecode = "00XX";
-        assertThatThrownBy(() -> {
-            final AlphabetConverter ac = createJavadocExample();
-            ac.decode(toDecode);
-        }).isInstanceOf(UnsupportedEncodingException.class).hasMessage("Unexpected string without decoding (XX) in " + toDecode);
+        assertEquals("Unexpected string without decoding (XX) in " + toDecode,
+                assertThrows(UnsupportedEncodingException.class, () -> createJavadocExample().decode(toDecode)).getMessage());
     }
 
     /**
@@ -287,14 +285,11 @@ public class AlphabetConverterTest {
     @Test
     public void testUnicodeTest() throws UnsupportedEncodingException {
         final AlphabetConverter ac = AlphabetConverter.createConverter(UNICODE, LOWER_CASE_ENGLISH_CODEPOINTS, DO_NOT_ENCODE_CODEPOINTS);
-
-        assertThat(ac.getEncodedCharLength()).isEqualTo(2);
-
+        assertEquals(2, ac.getEncodedCharLength());
         final String original = "\u8a43\u8a45 \u8dce ab \u8dc3 c \u8983";
         final String encoded = ac.encode(original);
         final String decoded = ac.decode(encoded);
-
-        assertThat(decoded).as("Encoded '" + original + "' into '" + encoded + "', but decoded into '" + decoded + "'").isEqualTo(original);
+        assertEquals(original, decoded, () -> "Encoded '" + original + "' into '" + encoded + "', but decoded into '" + decoded + "'");
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/CaseUtilsTest.java b/src/test/java/org/apache/commons/text/CaseUtilsTest.java
index f7195e70..78a6c549 100644
--- a/src/test/java/org/apache/commons/text/CaseUtilsTest.java
+++ b/src/test/java/org/apache/commons/text/CaseUtilsTest.java
@@ -16,7 +16,11 @@
  */
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Modifier;
@@ -30,47 +34,47 @@ public class CaseUtilsTest {
 
     @Test
     public void testConstructor() {
-        assertThat(new CaseUtils()).isNotNull();
+        assertNotNull(new CaseUtils());
         final Constructor<?>[] cons = CaseUtils.class.getDeclaredConstructors();
-        assertThat(cons.length).isEqualTo(1);
-        assertThat(Modifier.isPublic(cons[0].getModifiers())).isTrue();
-        assertThat(Modifier.isPublic(CaseUtils.class.getModifiers())).isTrue();
-        assertThat(Modifier.isFinal(CaseUtils.class.getModifiers())).isFalse();
+        assertEquals(1, cons.length);
+        assertTrue(Modifier.isPublic(cons[0].getModifiers()));
+        assertTrue(Modifier.isPublic(CaseUtils.class.getModifiers()));
+        assertFalse(Modifier.isFinal(CaseUtils.class.getModifiers()));
     }
 
     @Test
     public void testToCamelCase() {
-        assertThat(CaseUtils.toCamelCase(null, false, null)).isNull();
-        assertThat(CaseUtils.toCamelCase("", true, null)).isEqualTo("");
-        assertThat(CaseUtils.toCamelCase("  ", false, null)).isEqualTo("");
-        assertThat(CaseUtils.toCamelCase("a  b  c  @def", false, null)).isEqualTo("aBC@def");
-        assertThat(CaseUtils.toCamelCase("a b c @def", true)).isEqualTo("ABC@def");
-        assertThat(CaseUtils.toCamelCase("a b c @def", true, '-')).isEqualTo("ABC@def");
-        assertThat(CaseUtils.toCamelCase("a b c @def", true, '-')).isEqualTo("ABC@def");
+        assertNull(CaseUtils.toCamelCase(null, false, null));
+        assertEquals("", CaseUtils.toCamelCase("", true, null));
+        assertEquals("", CaseUtils.toCamelCase("  ", false, null));
+        assertEquals("aBC@def", CaseUtils.toCamelCase("a  b  c  @def", false, null));
+        assertEquals("ABC@def", CaseUtils.toCamelCase("a b c @def", true));
+        assertEquals("ABC@def", CaseUtils.toCamelCase("a b c @def", true, '-'));
+        assertEquals("ABC@def", CaseUtils.toCamelCase("a b c @def", true, '-'));
 
-        final char[] chars = {'-', '+', ' ', '@'};
-        assertThat(CaseUtils.toCamelCase("-+@ ", true, chars)).isEqualTo("");
-        assertThat(CaseUtils.toCamelCase("   to-CAMEL-cASE", false, chars)).isEqualTo("toCamelCase");
-        assertThat(CaseUtils.toCamelCase("@@@@   to+CAMEL@cASE ", true, chars)).isEqualTo("ToCamelCase");
-        assertThat(CaseUtils.toCamelCase("To+CA+ME L@cASE", true, chars)).isEqualTo("ToCaMeLCase");
+        final char[] chars = { '-', '+', ' ', '@' };
+        assertEquals("", CaseUtils.toCamelCase("-+@ ", true, chars));
+        assertEquals("toCamelCase", CaseUtils.toCamelCase("   to-CAMEL-cASE", false, chars));
+        assertEquals("ToCamelCase", CaseUtils.toCamelCase("@@@@   to+CAMEL@cASE ", true, chars));
+        assertEquals("ToCaMeLCase", CaseUtils.toCamelCase("To+CA+ME L@cASE", true, chars));
 
-        assertThat(CaseUtils.toCamelCase("To.Camel.Case", false, '.')).isEqualTo("toCamelCase");
-        assertThat(CaseUtils.toCamelCase("To.Camel-Case", false, '-', '.')).isEqualTo("toCamelCase");
-        assertThat(CaseUtils.toCamelCase(" to @ Camel case", false, '-', '@')).isEqualTo("toCamelCase");
-        assertThat(CaseUtils.toCamelCase(" @to @ Camel case", true, '-', '@')).isEqualTo("ToCamelCase");
+        assertEquals("toCamelCase", CaseUtils.toCamelCase("To.Camel.Case", false, '.'));
+        assertEquals("toCamelCase", CaseUtils.toCamelCase("To.Camel-Case", false, '-', '.'));
+        assertEquals("toCamelCase", CaseUtils.toCamelCase(" to @ Camel case", false, '-', '@'));
+        assertEquals("ToCamelCase", CaseUtils.toCamelCase(" @to @ Camel case", true, '-', '@'));
 
-        assertThat(CaseUtils.toCamelCase("TO CAMEL CASE", true, null)).isEqualTo("ToCamelCase");
-        assertThat(CaseUtils.toCamelCase("TO CAMEL CASE", false, null)).isEqualTo("toCamelCase");
-        assertThat(CaseUtils.toCamelCase("TO CAMEL CASE", false, null)).isEqualTo("toCamelCase");
-        assertThat(CaseUtils.toCamelCase("tocamelcase", false, null)).isEqualTo("tocamelcase");
-        assertThat(CaseUtils.toCamelCase("tocamelcase", true, null)).isEqualTo("Tocamelcase");
-        assertThat(CaseUtils.toCamelCase("Tocamelcase", false, null)).isEqualTo("tocamelcase");
+        assertEquals("ToCamelCase", CaseUtils.toCamelCase("TO CAMEL CASE", true, null));
+        assertEquals("toCamelCase", CaseUtils.toCamelCase("TO CAMEL CASE", false, null));
+        assertEquals("toCamelCase", CaseUtils.toCamelCase("TO CAMEL CASE", false, null));
+        assertEquals("tocamelcase", CaseUtils.toCamelCase("tocamelcase", false, null));
+        assertEquals("Tocamelcase", CaseUtils.toCamelCase("tocamelcase", true, null));
+        assertEquals("tocamelcase", CaseUtils.toCamelCase("Tocamelcase", false, null));
 
-        assertThat(CaseUtils.toCamelCase("tocamelcase", true)).isEqualTo("Tocamelcase");
-        assertThat(CaseUtils.toCamelCase("tocamelcase", false)).isEqualTo("tocamelcase");
+        assertEquals("Tocamelcase", CaseUtils.toCamelCase("tocamelcase", true));
+        assertEquals("tocamelcase", CaseUtils.toCamelCase("tocamelcase", false));
 
-        assertThat(CaseUtils.toCamelCase("\uD800\uDF00 \uD800\uDF02", true)).isEqualTo("\uD800\uDF00\uD800\uDF02");
-        assertThat(CaseUtils.toCamelCase("\uD800\uDF00\uD800\uDF01\uD800\uDF14\uD800\uDF02\uD800\uDF03", true, '\uD800',
-            '\uDF14')).isEqualTo("\uD800\uDF00\uD800\uDF01\uD800\uDF02\uD800\uDF03");
+        assertEquals("\uD800\uDF00\uD800\uDF02", CaseUtils.toCamelCase("\uD800\uDF00 \uD800\uDF02", true));
+        assertEquals("\uD800\uDF00\uD800\uDF01\uD800\uDF02\uD800\uDF03",
+                CaseUtils.toCamelCase("\uD800\uDF00\uD800\uDF01\uD800\uDF14\uD800\uDF02\uD800\uDF03", true, '\uD800', '\uDF14'));
     }
 }
diff --git a/src/test/java/org/apache/commons/text/CharacterPredicatesTest.java b/src/test/java/org/apache/commons/text/CharacterPredicatesTest.java
index 4a53c6b3..815ff13e 100644
--- a/src/test/java/org/apache/commons/text/CharacterPredicatesTest.java
+++ b/src/test/java/org/apache/commons/text/CharacterPredicatesTest.java
@@ -16,7 +16,8 @@
  */
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import org.junit.jupiter.api.Test;
 
@@ -27,87 +28,87 @@ public class CharacterPredicatesTest {
 
     @Test
     public void testArabicNumerals() {
-        assertThat(CharacterPredicates.ARABIC_NUMERALS.test('0')).isTrue();
-        assertThat(CharacterPredicates.ARABIC_NUMERALS.test('1')).isTrue();
-        assertThat(CharacterPredicates.ARABIC_NUMERALS.test('9')).isTrue();
+        assertTrue(CharacterPredicates.ARABIC_NUMERALS.test('0'));
+        assertTrue(CharacterPredicates.ARABIC_NUMERALS.test('1'));
+        assertTrue(CharacterPredicates.ARABIC_NUMERALS.test('9'));
 
-        assertThat(CharacterPredicates.ARABIC_NUMERALS.test('/')).isFalse();
-        assertThat(CharacterPredicates.ARABIC_NUMERALS.test(':')).isFalse();
-        assertThat(CharacterPredicates.ARABIC_NUMERALS.test('a')).isFalse();
+        assertFalse(CharacterPredicates.ARABIC_NUMERALS.test('/'));
+        assertFalse(CharacterPredicates.ARABIC_NUMERALS.test(':'));
+        assertFalse(CharacterPredicates.ARABIC_NUMERALS.test('a'));
     }
 
     @Test
     public void testAsciiAlphaNumerals() {
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('a')).isTrue();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('z')).isTrue();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('A')).isTrue();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('Z')).isTrue();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('0')).isTrue();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('9')).isTrue();
-
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('`')).isFalse();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('{')).isFalse();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('@')).isFalse();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('[')).isFalse();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('/')).isFalse();
-        assertThat(CharacterPredicates.ASCII_ALPHA_NUMERALS.test(':')).isFalse();
+        assertTrue(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('a'));
+        assertTrue(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('z'));
+        assertTrue(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('A'));
+        assertTrue(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('Z'));
+        assertTrue(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('0'));
+        assertTrue(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('9'));
+
+        assertFalse(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('`'));
+        assertFalse(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('{'));
+        assertFalse(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('@'));
+        assertFalse(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('['));
+        assertFalse(CharacterPredicates.ASCII_ALPHA_NUMERALS.test('/'));
+        assertFalse(CharacterPredicates.ASCII_ALPHA_NUMERALS.test(':'));
     }
 
     @Test
     public void testAsciiLetters() {
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('a')).isTrue();
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('z')).isTrue();
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('A')).isTrue();
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('Z')).isTrue();
-
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('9')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('`')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('{')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('@')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LETTERS.test('[')).isFalse();
+        assertTrue(CharacterPredicates.ASCII_LETTERS.test('a'));
+        assertTrue(CharacterPredicates.ASCII_LETTERS.test('z'));
+        assertTrue(CharacterPredicates.ASCII_LETTERS.test('A'));
+        assertTrue(CharacterPredicates.ASCII_LETTERS.test('Z'));
+
+        assertFalse(CharacterPredicates.ASCII_LETTERS.test('9'));
+        assertFalse(CharacterPredicates.ASCII_LETTERS.test('`'));
+        assertFalse(CharacterPredicates.ASCII_LETTERS.test('{'));
+        assertFalse(CharacterPredicates.ASCII_LETTERS.test('@'));
+        assertFalse(CharacterPredicates.ASCII_LETTERS.test('['));
     }
 
     @Test
     public void testAsciiLowercaseLetters() {
-        assertThat(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('a')).isTrue();
-        assertThat(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('z')).isTrue();
-
-        assertThat(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('9')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('A')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('Z')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('`')).isFalse();
-        assertThat(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('{')).isFalse();
+        assertTrue(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('a'));
+        assertTrue(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('z'));
+
+        assertFalse(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('9'));
+        assertFalse(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('A'));
+        assertFalse(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('Z'));
+        assertFalse(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('`'));
+        assertFalse(CharacterPredicates.ASCII_LOWERCASE_LETTERS.test('{'));
     }
 
     @Test
     public void testAsciiUppercaseLetters() {
-        assertThat(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('A')).isTrue();
-        assertThat(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('Z')).isTrue();
-
-        assertThat(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('9')).isFalse();
-        assertThat(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('@')).isFalse();
-        assertThat(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('[')).isFalse();
-        assertThat(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('a')).isFalse();
-        assertThat(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('z')).isFalse();
+        assertTrue(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('A'));
+        assertTrue(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('Z'));
+
+        assertFalse(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('9'));
+        assertFalse(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('@'));
+        assertFalse(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('['));
+        assertFalse(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('a'));
+        assertFalse(CharacterPredicates.ASCII_UPPERCASE_LETTERS.test('z'));
     }
 
     @Test
     public void testDigits() {
-        assertThat(CharacterPredicates.DIGITS.test('0')).isTrue();
-        assertThat(CharacterPredicates.DIGITS.test('9')).isTrue();
+        assertTrue(CharacterPredicates.DIGITS.test('0'));
+        assertTrue(CharacterPredicates.DIGITS.test('9'));
 
-        assertThat(CharacterPredicates.DIGITS.test('-')).isFalse();
-        assertThat(CharacterPredicates.DIGITS.test('.')).isFalse();
-        assertThat(CharacterPredicates.DIGITS.test('L')).isFalse();
+        assertFalse(CharacterPredicates.DIGITS.test('-'));
+        assertFalse(CharacterPredicates.DIGITS.test('.'));
+        assertFalse(CharacterPredicates.DIGITS.test('L'));
     }
 
     @Test
     public void testLetters() {
-        assertThat(CharacterPredicates.LETTERS.test('a')).isTrue();
-        assertThat(CharacterPredicates.LETTERS.test('Z')).isTrue();
+        assertTrue(CharacterPredicates.LETTERS.test('a'));
+        assertTrue(CharacterPredicates.LETTERS.test('Z'));
 
-        assertThat(CharacterPredicates.LETTERS.test('1')).isFalse();
-        assertThat(CharacterPredicates.LETTERS.test('?')).isFalse();
-        assertThat(CharacterPredicates.LETTERS.test('@')).isFalse();
+        assertFalse(CharacterPredicates.LETTERS.test('1'));
+        assertFalse(CharacterPredicates.LETTERS.test('?'));
+        assertFalse(CharacterPredicates.LETTERS.test('@'));
     }
 }
diff --git a/src/test/java/org/apache/commons/text/ExtendedMessageFormatTest.java b/src/test/java/org/apache/commons/text/ExtendedMessageFormatTest.java
index b718dcf5..20d6e4a8 100644
--- a/src/test/java/org/apache/commons/text/ExtendedMessageFormatTest.java
+++ b/src/test/java/org/apache/commons/text/ExtendedMessageFormatTest.java
@@ -16,10 +16,9 @@
  */
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertThrowsExactly;
 
 import java.text.DateFormat;
 import java.text.FieldPosition;
@@ -68,8 +67,7 @@ public class ExtendedMessageFormatTest {
     private static final class OtherExtendedMessageFormat extends ExtendedMessageFormat {
         private static final long serialVersionUID = 1L;
 
-        OtherExtendedMessageFormat(final String pattern, final Locale locale,
-                final Map<String, ? extends FormatFactory> registry) {
+        OtherExtendedMessageFormat(final String pattern, final Locale locale, final Map<String, ? extends FormatFactory> registry) {
             super(pattern, locale, registry);
         }
     }
@@ -79,9 +77,7 @@ public class ExtendedMessageFormatTest {
      */
     private static final class OverrideShortDateFormatFactory {
         static final FormatFactory FACTORY = (n, a, l) -> !"short".equals(a) ? null
-                : l == null ? DateFormat
-                        .getDateInstance(DateFormat.DEFAULT) : DateFormat
-                        .getDateInstance(DateFormat.DEFAULT, l);
+                : l == null ? DateFormat.getDateInstance(DateFormat.DEFAULT) : DateFormat.getDateInstance(DateFormat.DEFAULT, l);
     }
 
     /**
@@ -106,15 +102,14 @@ public class ExtendedMessageFormatTest {
     private final Map<String, FormatFactory> registry = new HashMap<>();
 
     /**
-     * Create an ExtendedMessageFormat for the specified pattern and locale and check the
-     * formatted output matches the expected result for the parameters.
-     * @param pattern string
+     * Create an ExtendedMessageFormat for the specified pattern and locale and check the formatted output matches the expected result for the parameters.
+     *
+     * @param pattern        string
      * @param registryUnused map (currently unused)
-     * @param args Object[]
-     * @param locale Locale
+     * @param args           Object[]
+     * @param locale         Locale
      */
-    private void checkBuiltInFormat(final String pattern, final Map<String, ?> registryUnused, final Object[] args,
-            final Locale locale) {
+    private void checkBuiltInFormat(final String pattern, final Map<String, ?> registryUnused, final Object[] args, final Locale locale) {
         final StringBuilder buffer = new StringBuilder();
         buffer.append("Pattern=[");
         buffer.append(pattern);
@@ -129,7 +124,7 @@ public class ExtendedMessageFormatTest {
         } else {
             emf = new ExtendedMessageFormat(pattern, locale);
         }
-        assertEquals(mf.format(args), emf.format(args), "format "    + buffer.toString());
+        assertEquals(mf.format(args), emf.format(args), "format " + buffer.toString());
         assertEquals(mf.toPattern(), emf.toPattern(), "toPattern " + buffer.toString());
     }
 
@@ -190,13 +185,13 @@ public class ExtendedMessageFormatTest {
 
     /**
      * Test a built in format for the specified Locales, plus {@code null} Locale.
-     * @param pattern MessageFormat pattern
+     *
+     * @param pattern     MessageFormat pattern
      * @param fmtRegistry FormatFactory registry to use
-     * @param args MessageFormat arguments
-     * @param locales to test
+     * @param args        MessageFormat arguments
+     * @param locales     to test
      */
-    private void checkBuiltInFormat(final String pattern, final Map<String, ?> fmtRegistry, final Object[] args,
-            final Locale[] locales) {
+    private void checkBuiltInFormat(final String pattern, final Map<String, ?> fmtRegistry, final Object[] args, final Locale[] locales) {
         checkBuiltInFormat(pattern, fmtRegistry, args, (Locale) null);
         for (final Locale locale : locales) {
             checkBuiltInFormat(pattern, fmtRegistry, args, locale);
@@ -205,8 +200,9 @@ public class ExtendedMessageFormatTest {
 
     /**
      * Test a built in format for the specified Locales, plus {@code null} Locale.
+     *
      * @param pattern MessageFormat pattern
-     * @param args MessageFormat arguments
+     * @param args    MessageFormat arguments
      * @param locales to test
      */
     private void checkBuiltInFormat(final String pattern, final Object[] args, final Locale[] locales) {
@@ -215,8 +211,9 @@ public class ExtendedMessageFormatTest {
 
     /**
      * Replace MessageFormat(String, Locale) constructor (not available until JDK 1.4).
+     *
      * @param pattern string
-     * @param locale Locale
+     * @param locale  Locale
      * @return MessageFormat
      */
     private MessageFormat createMessageFormat(final String pattern, final Locale locale) {
@@ -239,18 +236,18 @@ public class ExtendedMessageFormatTest {
      */
     @Test
     public void testBuiltInChoiceFormat() {
-        final Object[] values = new Number[] {1, Double.valueOf("2.2"), Double.valueOf("1234.5")};
+        final Object[] values = new Number[] { 1, Double.valueOf("2.2"), Double.valueOf("1234.5") };
         String choicePattern;
         final Locale[] availableLocales = NumberFormat.getAvailableLocales();
 
         choicePattern = "{0,choice,1#One|2#Two|3#Many {0,number}}";
         for (final Object value : values) {
-            checkBuiltInFormat(value + ": " + choicePattern, new Object[] {value}, availableLocales);
+            checkBuiltInFormat(value + ": " + choicePattern, new Object[] { value }, availableLocales);
         }
 
         choicePattern = "{0,choice,1#''One''|2#\"Two\"|3#''{Many}'' {0,number}}";
         for (final Object value : values) {
-            checkBuiltInFormat(value + ": " + choicePattern, new Object[] {value}, availableLocales);
+            checkBuiltInFormat(value + ": " + choicePattern, new Object[] { value }, availableLocales);
         }
     }
 
@@ -261,21 +258,21 @@ public class ExtendedMessageFormatTest {
     public void testBuiltInDateTimeFormat() {
         final Calendar cal = Calendar.getInstance();
         cal.set(2007, Calendar.JANUARY, 23, 18, 33, 5);
-        final Object[] args = {cal.getTime()};
+        final Object[] args = { cal.getTime() };
         final Locale[] availableLocales = DateFormat.getAvailableLocales();
 
-        checkBuiltInFormat("1: {0,date,short}",    args, availableLocales);
-        checkBuiltInFormat("2: {0,date,medium}",   args, availableLocales);
-        checkBuiltInFormat("3: {0,date,long}",     args, availableLocales);
-        checkBuiltInFormat("4: {0,date,full}",     args, availableLocales);
+        checkBuiltInFormat("1: {0,date,short}", args, availableLocales);
+        checkBuiltInFormat("2: {0,date,medium}", args, availableLocales);
+        checkBuiltInFormat("3: {0,date,long}", args, availableLocales);
+        checkBuiltInFormat("4: {0,date,full}", args, availableLocales);
         checkBuiltInFormat("5: {0,date,d MMM yy}", args, availableLocales);
-        checkBuiltInFormat("6: {0,time,short}",    args, availableLocales);
-        checkBuiltInFormat("7: {0,time,medium}",   args, availableLocales);
-        checkBuiltInFormat("8: {0,time,long}",     args, availableLocales);
-        checkBuiltInFormat("9: {0,time,full}",     args, availableLocales);
-        checkBuiltInFormat("10: {0,time,HH:mm}",   args, availableLocales);
-        checkBuiltInFormat("11: {0,date}",         args, availableLocales);
-        checkBuiltInFormat("12: {0,time}",         args, availableLocales);
+        checkBuiltInFormat("6: {0,time,short}", args, availableLocales);
+        checkBuiltInFormat("7: {0,time,medium}", args, availableLocales);
+        checkBuiltInFormat("8: {0,time,long}", args, availableLocales);
+        checkBuiltInFormat("9: {0,time,full}", args, availableLocales);
+        checkBuiltInFormat("10: {0,time,HH:mm}", args, availableLocales);
+        checkBuiltInFormat("11: {0,date}", args, availableLocales);
+        checkBuiltInFormat("12: {0,time}", args, availableLocales);
     }
 
     /**
@@ -283,34 +280,31 @@ public class ExtendedMessageFormatTest {
      */
     @Test
     public void testBuiltInNumberFormat() {
-        final Object[] args = {Double.valueOf("6543.21")};
+        final Object[] args = { Double.valueOf("6543.21") };
         final Locale[] availableLocales = NumberFormat.getAvailableLocales();
-        checkBuiltInFormat("1: {0,number}",           args, availableLocales);
-        checkBuiltInFormat("2: {0,number,integer}",   args, availableLocales);
-        checkBuiltInFormat("3: {0,number,currency}",  args, availableLocales);
-        checkBuiltInFormat("4: {0,number,percent}",   args, availableLocales);
+        checkBuiltInFormat("1: {0,number}", args, availableLocales);
+        checkBuiltInFormat("2: {0,number,integer}", args, availableLocales);
+        checkBuiltInFormat("3: {0,number,currency}", args, availableLocales);
+        checkBuiltInFormat("4: {0,number,percent}", args, availableLocales);
         checkBuiltInFormat("5: {0,number,00000.000}", args, availableLocales);
     }
 
     /**
-     * Test Bug TEXT-106 - Exception while using ExtendedMessageFormat and choice format element with quote just
-     * before brace end
+     * Test Bug TEXT-106 - Exception while using ExtendedMessageFormat and choice format element with quote just before brace end
      */
     @Test
     public void testChoiceQuoteJustBeforeBraceEnd_TEXT_106() {
         final String pattern2 = "Choice format element with quote just before brace end ''{0,choice,0#0|0<'1'}''";
         final ExtendedMessageFormat emf = new ExtendedMessageFormat(pattern2, registry);
-        assertEquals("Choice format element with quote just before brace end '0'", emf.format(new Object[] {0}));
-        assertEquals("Choice format element with quote just before brace end '1'", emf.format(new Object[] {1}));
+        assertEquals("Choice format element with quote just before brace end '0'", emf.format(new Object[] { 0 }));
+        assertEquals("Choice format element with quote just before brace end '1'", emf.format(new Object[] { 1 }));
     }
 
     @Test
     public void testCreatesExtendedMessageFormatTakingString() {
-        final ExtendedMessageFormat extendedMessageFormat =
-                new ExtendedMessageFormat("Unterminated format element at position ");
+        final ExtendedMessageFormat extendedMessageFormat = new ExtendedMessageFormat("Unterminated format element at position ");
         final Map<String, FormatFactory> map = new HashMap<>();
-        final ExtendedMessageFormat extendedMessageFormatTwo =
-                new ExtendedMessageFormat("Unterminated format element at position ", map);
+        final ExtendedMessageFormat extendedMessageFormatTwo = new ExtendedMessageFormat("Unterminated format element at position ", map);
 
         assertEquals("Unterminated format element at position ", extendedMessageFormatTwo.toPattern());
         assertNotEquals(extendedMessageFormat, extendedMessageFormatTwo);
@@ -323,7 +317,7 @@ public class ExtendedMessageFormatTest {
     public void testEmbeddedPatternInChoice() {
         final String pattern = "Hi {0,lower}, got {1,choice,0#none|1#one|1<{1,number}}, {2,upper}!";
         final ExtendedMessageFormat emf = new ExtendedMessageFormat(pattern, registry);
-        assertEquals("Hi there, got 3, GREAT!", emf.format(new Object[] {"there", 3, "great"}));
+        assertEquals("Hi there, got 3, GREAT!", emf.format(new Object[] { "there", 3, "great" }));
     }
 
     /**
@@ -331,10 +325,8 @@ public class ExtendedMessageFormatTest {
      */
     @Test
     public void testEqualsHashcode() {
-        final Map<String, ? extends FormatFactory> fmtRegistry =
-                Collections.singletonMap("testfmt", LowerCaseFormat.FACTORY);
-        final Map<String, ? extends FormatFactory> otherRegistry =
-                Collections.singletonMap("testfmt", UpperCaseFormat.FACTORY);
+        final Map<String, ? extends FormatFactory> fmtRegistry = Collections.singletonMap("testfmt", LowerCaseFormat.FACTORY);
+        final Map<String, ? extends FormatFactory> otherRegistry = Collections.singletonMap("testfmt", UpperCaseFormat.FACTORY);
 
         final String pattern = "Pattern: {0,testfmt}";
         final ExtendedMessageFormat emf = new ExtendedMessageFormat(pattern, Locale.US, fmtRegistry);
@@ -381,12 +373,12 @@ public class ExtendedMessageFormatTest {
         // message without placeholder because braces are escaped by quotes
         final String pattern = "Message without placeholders '{}'";
         final ExtendedMessageFormat emf = new ExtendedMessageFormat(pattern, registry);
-        assertEquals("Message without placeholders {}", emf.format(new Object[] {"DUMMY"}));
+        assertEquals("Message without placeholders {}", emf.format(new Object[] { "DUMMY" }));
 
         // message with placeholder because quotes are escaped by quotes
         final String pattern2 = "Message with placeholder ''{0}''";
         final ExtendedMessageFormat emf2 = new ExtendedMessageFormat(pattern2, registry);
-        assertEquals("Message with placeholder 'DUMMY'", emf2.format(new Object[] {"DUMMY"}));
+        assertEquals("Message with placeholder 'DUMMY'", emf2.format(new Object[] { "DUMMY" }));
     }
 
     /**
@@ -396,7 +388,7 @@ public class ExtendedMessageFormatTest {
     public void testEscapedQuote_LANG_477() {
         final String pattern = "it''s a {0,lower} 'test'!";
         final ExtendedMessageFormat emf = new ExtendedMessageFormat(pattern, registry);
-        assertEquals("it's a dummy test!", emf.format(new Object[] {"DUMMY"}));
+        assertEquals("it's a dummy test!", emf.format(new Object[] { "DUMMY" }));
     }
 
     /**
@@ -406,7 +398,7 @@ public class ExtendedMessageFormatTest {
     public void testExtendedAndBuiltInFormats() {
         final Calendar cal = Calendar.getInstance();
         cal.set(2007, Calendar.JANUARY, 23, 18, 33, 5);
-        final Object[] args = {"John Doe", cal.getTime(), Double.valueOf("12345.67")};
+        final Object[] args = { "John Doe", cal.getTime(), Double.valueOf("12345.67") };
         final String builtinsPattern = "DOB: {1,date,short} Salary: {2,number,currency}";
         final String extendedPattern = "Name: {0,upper} ";
         final String pattern = extendedPattern + builtinsPattern;
@@ -450,36 +442,36 @@ public class ExtendedMessageFormatTest {
         final String pattern = "Lower: {0,lower} Upper: {1,upper}";
         final ExtendedMessageFormat emf = new ExtendedMessageFormat(pattern, registry);
         assertEquals(pattern, emf.toPattern(), "TOPATTERN");
-        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] {"foo", "bar"}));
-        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] {"Foo", "Bar"}));
-        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] {"FOO", "BAR"}));
-        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] {"FOO", "bar"}));
-        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] {"foo", "BAR"}));
+        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] { "foo", "bar" }));
+        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] { "Foo", "Bar" }));
+        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] { "FOO", "BAR" }));
+        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] { "FOO", "bar" }));
+        assertEquals("Lower: foo Upper: BAR", emf.format(new Object[] { "foo", "BAR" }));
     }
 
     @Test
     public void testFailsToCreateExtendedMessageFormatTakingTwoArgumentsThrowsIllegalArgumentExceptionFive() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new ExtendedMessageFormat("j/[_D9{0,\"&'+0o", new HashMap<>()));
+        assertThrowsExactly(IllegalArgumentException.class, () -> new ExtendedMessageFormat("j/[_D9{0,\"&'+0o", new HashMap<>()));
     }
 
     @Test
     public void testFailsToCreateExtendedMessageFormatTakingTwoArgumentsThrowsIllegalArgumentExceptionFour() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new ExtendedMessageFormat("RD,nXhM{}{", new HashMap<>()));
+        assertThrowsExactly(IllegalArgumentException.class, () -> new ExtendedMessageFormat("RD,nXhM{}{", new HashMap<>()));
     }
 
     @Test
     public void testFailsToCreateExtendedMessageFormatTakingTwoArgumentsThrowsIllegalArgumentExceptionOne() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new ExtendedMessageFormat("agdXdkR;T1{9 ^,LzXf?", new HashMap<>()));
+        assertThrowsExactly(IllegalArgumentException.class, () -> new ExtendedMessageFormat("agdXdkR;T1{9 ^,LzXf?", new HashMap<>()));
     }
 
     @Test
     public void testFailsToCreateExtendedMessageFormatTakingTwoArgumentsThrowsIllegalArgumentExceptionThree() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new ExtendedMessageFormat("9jLh_D9{ ", new HashMap<>()));
+        assertThrowsExactly(IllegalArgumentException.class, () -> new ExtendedMessageFormat("9jLh_D9{ ", new HashMap<>()));
     }
 
     @Test
     public void testFailsToCreateExtendedMessageFormatTakingTwoArgumentsThrowsIllegalArgumentExceptionTwo() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new ExtendedMessageFormat("a5XdkR;T1{9 ,LzXf?", new HashMap<>()));
+        assertThrowsExactly(IllegalArgumentException.class, () -> new ExtendedMessageFormat("a5XdkR;T1{9 ,LzXf?", new HashMap<>()));
     }
 
     @Test
@@ -510,32 +502,24 @@ public class ExtendedMessageFormatTest {
 
     @Test
     public void testSetFormatByArgumentIndexIsUnsupported() {
-        assertThatExceptionOfType(UnsupportedOperationException.class).isThrownBy(() -> {
-            final ExtendedMessageFormat emf = new ExtendedMessageFormat("");
-            emf.setFormatByArgumentIndex(0, new LowerCaseFormat());
-        });
+        assertThrowsExactly(UnsupportedOperationException.class, () -> new ExtendedMessageFormat("").setFormatByArgumentIndex(0, new LowerCaseFormat()));
     }
+
     @Test
     public void testSetFormatIsUnsupported() {
-        assertThatExceptionOfType(UnsupportedOperationException.class).isThrownBy(() -> {
-            final ExtendedMessageFormat emf = new ExtendedMessageFormat("");
-            emf.setFormat(0, new LowerCaseFormat());
-        });
+        assertThrowsExactly(UnsupportedOperationException.class, () -> new ExtendedMessageFormat("").setFormat(0, new LowerCaseFormat()));
     }
+
     @Test
     public void testSetFormatsByArgumentIndex() {
-        assertThatExceptionOfType(UnsupportedOperationException.class).isThrownBy(() -> {
-            final ExtendedMessageFormat emf = new ExtendedMessageFormat("");
-            emf.setFormatsByArgumentIndex(new Format[] {new LowerCaseFormat(), new UpperCaseFormat()});
-        });
+        assertThrowsExactly(UnsupportedOperationException.class,
+                () -> new ExtendedMessageFormat("").setFormatsByArgumentIndex(new Format[] { new LowerCaseFormat(), new UpperCaseFormat() }));
     }
 
     @Test
     public void testSetFormatsIsUnsupported() {
-        assertThatExceptionOfType(UnsupportedOperationException.class).isThrownBy(() -> {
-            final ExtendedMessageFormat emf = new ExtendedMessageFormat("");
-            emf.setFormats(new Format[] {new LowerCaseFormat(), new UpperCaseFormat()});
-        });
+        assertThrowsExactly(UnsupportedOperationException.class,
+                () -> new ExtendedMessageFormat("").setFormats(new Format[] { new LowerCaseFormat(), new UpperCaseFormat() }));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/FormattableUtilsTest.java b/src/test/java/org/apache/commons/text/FormattableUtilsTest.java
index b6008ee1..483096a8 100644
--- a/src/test/java/org/apache/commons/text/FormattableUtilsTest.java
+++ b/src/test/java/org/apache/commons/text/FormattableUtilsTest.java
@@ -17,9 +17,8 @@
 package org.apache.commons.text;
 
 import static java.util.FormattableFlags.LEFT_JUSTIFY;
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
-import static org.assertj.core.api.Assertions.assertThatNullPointerException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrowsExactly;
 
 import java.util.Formattable;
 import java.util.Formatter;
@@ -51,98 +50,98 @@ public class FormattableUtilsTest {
     @Test
     public void testAlternatePadCharacter() {
         final char pad = '_';
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, -1, pad).toString()).isEqualTo("foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, 2, pad).toString()).isEqualTo("fo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 4, -1, pad).toString()).isEqualTo("_foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 6, -1, pad).toString()).isEqualTo("___foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 3, 2, pad).toString()).isEqualTo("_fo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 5, 2, pad).toString()).isEqualTo("___fo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, pad).toString()).isEqualTo("foo_");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, pad).toString()).isEqualTo("foo___");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, pad).toString()).isEqualTo("fo_");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, pad).toString()).isEqualTo("fo___");
+        assertEquals("foo", FormattableUtils.append("foo", createFormatter(), 0, -1, -1, pad).toString());
+        assertEquals("fo", FormattableUtils.append("foo", createFormatter(), 0, -1, 2, pad).toString());
+        assertEquals("_foo", FormattableUtils.append("foo", createFormatter(), 0, 4, -1, pad).toString());
+        assertEquals("___foo", FormattableUtils.append("foo", createFormatter(), 0, 6, -1, pad).toString());
+        assertEquals("_fo", FormattableUtils.append("foo", createFormatter(), 0, 3, 2, pad).toString());
+        assertEquals("___fo", FormattableUtils.append("foo", createFormatter(), 0, 5, 2, pad).toString());
+        assertEquals("foo_", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, pad).toString());
+        assertEquals("foo___", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, pad).toString());
+        assertEquals("fo_", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, pad).toString());
+        assertEquals("fo___", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, pad).toString());
     }
 
     @Test
     public void testAlternatePadCharAndEllipsis() {
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, -1, '_', "*").toString()).isEqualTo("foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, 2, '_', "*").toString()).isEqualTo("f*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 4, -1, '_', "*").toString()).isEqualTo("_foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 6, -1, '_', "*").toString()).isEqualTo("___foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 3, 2, '_', "*").toString()).isEqualTo("_f*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 5, 2, '_', "*").toString()).isEqualTo("___f*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, '_', "*").toString()).isEqualTo("foo_");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, '_', "*").toString()).isEqualTo("foo___");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, '_', "*").toString()).isEqualTo("f*_");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, '_', "*").toString()).isEqualTo("f*___");
-
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, -1, '_', "+*").toString()).isEqualTo("foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, 2, '_', "+*").toString()).isEqualTo("+*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 4, -1, '_', "+*").toString()).isEqualTo("_foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 6, -1, '_', "+*").toString()).isEqualTo("___foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 3, 2, '_', "+*").toString()).isEqualTo("_+*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 5, 2, '_', "+*").toString()).isEqualTo("___+*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, '_', "+*").toString()).isEqualTo("foo_");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, '_', "+*").toString()).isEqualTo("foo___");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, '_', "+*").toString()).isEqualTo("+*_");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, '_', "+*").toString()).isEqualTo("+*___");
+        assertEquals("foo", FormattableUtils.append("foo", createFormatter(), 0, -1, -1, '_', "*").toString());
+        assertEquals("f*", FormattableUtils.append("foo", createFormatter(), 0, -1, 2, '_', "*").toString());
+        assertEquals("_foo", FormattableUtils.append("foo", createFormatter(), 0, 4, -1, '_', "*").toString());
+        assertEquals("___foo", FormattableUtils.append("foo", createFormatter(), 0, 6, -1, '_', "*").toString());
+        assertEquals("_f*", FormattableUtils.append("foo", createFormatter(), 0, 3, 2, '_', "*").toString());
+        assertEquals("___f*", FormattableUtils.append("foo", createFormatter(), 0, 5, 2, '_', "*").toString());
+        assertEquals("foo_", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, '_', "*").toString());
+        assertEquals("foo___", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, '_', "*").toString());
+        assertEquals("f*_", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, '_', "*").toString());
+        assertEquals("f*___", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, '_', "*").toString());
+
+        assertEquals("foo", FormattableUtils.append("foo", createFormatter(), 0, -1, -1, '_', "+*").toString());
+        assertEquals("+*", FormattableUtils.append("foo", createFormatter(), 0, -1, 2, '_', "+*").toString());
+        assertEquals("_foo", FormattableUtils.append("foo", createFormatter(), 0, 4, -1, '_', "+*").toString());
+        assertEquals("___foo", FormattableUtils.append("foo", createFormatter(), 0, 6, -1, '_', "+*").toString());
+        assertEquals("_+*", FormattableUtils.append("foo", createFormatter(), 0, 3, 2, '_', "+*").toString());
+        assertEquals("___+*", FormattableUtils.append("foo", createFormatter(), 0, 5, 2, '_', "+*").toString());
+        assertEquals("foo_", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, '_', "+*").toString());
+        assertEquals("foo___", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, '_', "+*").toString());
+        assertEquals("+*_", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, '_', "+*").toString());
+        assertEquals("+*___", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, '_', "+*").toString());
     }
 
     @Test
     public void testAppendWithNullFormatterAndIntsThrowsNullPointerException() {
-        assertThatNullPointerException().isThrownBy(() -> FormattableUtils.append("", null, 0, 0, 0, '}'));
+        assertThrowsExactly(NullPointerException.class, () -> FormattableUtils.append("", null, 0, 0, 0, '}'));
     }
 
     @Test
     public void testDefaultAppend() {
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, -1).toString()).isEqualTo("foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, 2).toString()).isEqualTo("fo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 4, -1).toString()).isEqualTo(" foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 6, -1).toString()).isEqualTo("   foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 3, 2).toString()).isEqualTo(" fo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 5, 2).toString()).isEqualTo("   fo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1).toString()).isEqualTo("foo ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1).toString()).isEqualTo("foo   ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2).toString()).isEqualTo("fo ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2).toString()).isEqualTo("fo   ");
+        assertEquals("foo", FormattableUtils.append("foo", createFormatter(), 0, -1, -1).toString());
+        assertEquals("fo", FormattableUtils.append("foo", createFormatter(), 0, -1, 2).toString());
+        assertEquals(" foo", FormattableUtils.append("foo", createFormatter(), 0, 4, -1).toString());
+        assertEquals("   foo", FormattableUtils.append("foo", createFormatter(), 0, 6, -1).toString());
+        assertEquals(" fo", FormattableUtils.append("foo", createFormatter(), 0, 3, 2).toString());
+        assertEquals("   fo", FormattableUtils.append("foo", createFormatter(), 0, 5, 2).toString());
+        assertEquals("foo ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1).toString());
+        assertEquals("foo   ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1).toString());
+        assertEquals("fo ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2).toString());
+        assertEquals("fo   ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2).toString());
     }
 
     @Test
     public void testEllipsis() {
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, -1, "*").toString()).isEqualTo("foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, 2, "*").toString()).isEqualTo("f*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 4, -1, "*").toString()).isEqualTo(" foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 6, -1, "*").toString()).isEqualTo("   foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 3, 2, "*").toString()).isEqualTo(" f*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 5, 2, "*").toString()).isEqualTo("   f*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, "*").toString()).isEqualTo("foo ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, "*").toString()).isEqualTo("foo   ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, "*").toString()).isEqualTo("f* ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, "*").toString()).isEqualTo("f*   ");
-
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, -1, "+*").toString()).isEqualTo("foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, -1, 2, "+*").toString()).isEqualTo("+*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 4, -1, "+*").toString()).isEqualTo(" foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 6, -1, "+*").toString()).isEqualTo("   foo");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 3, 2, "+*").toString()).isEqualTo(" +*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), 0, 5, 2, "+*").toString()).isEqualTo("   +*");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, "+*").toString()).isEqualTo("foo ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, "+*").toString()).isEqualTo("foo   ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, "+*").toString()).isEqualTo("+* ");
-        assertThat(FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, "+*").toString()).isEqualTo("+*   ");
+        assertEquals("foo", FormattableUtils.append("foo", createFormatter(), 0, -1, -1, "*").toString());
+        assertEquals("f*", FormattableUtils.append("foo", createFormatter(), 0, -1, 2, "*").toString());
+        assertEquals(" foo", FormattableUtils.append("foo", createFormatter(), 0, 4, -1, "*").toString());
+        assertEquals("   foo", FormattableUtils.append("foo", createFormatter(), 0, 6, -1, "*").toString());
+        assertEquals(" f*", FormattableUtils.append("foo", createFormatter(), 0, 3, 2, "*").toString());
+        assertEquals("   f*", FormattableUtils.append("foo", createFormatter(), 0, 5, 2, "*").toString());
+        assertEquals("foo ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, "*").toString());
+        assertEquals("foo   ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, "*").toString());
+        assertEquals("f* ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, "*").toString());
+        assertEquals("f*   ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, "*").toString());
+
+        assertEquals("foo", FormattableUtils.append("foo", createFormatter(), 0, -1, -1, "+*").toString());
+        assertEquals("+*", FormattableUtils.append("foo", createFormatter(), 0, -1, 2, "+*").toString());
+        assertEquals(" foo", FormattableUtils.append("foo", createFormatter(), 0, 4, -1, "+*").toString());
+        assertEquals("   foo", FormattableUtils.append("foo", createFormatter(), 0, 6, -1, "+*").toString());
+        assertEquals(" +*", FormattableUtils.append("foo", createFormatter(), 0, 3, 2, "+*").toString());
+        assertEquals("   +*", FormattableUtils.append("foo", createFormatter(), 0, 5, 2, "+*").toString());
+        assertEquals("foo ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 4, -1, "+*").toString());
+        assertEquals("foo   ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 6, -1, "+*").toString());
+        assertEquals("+* ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 3, 2, "+*").toString());
+        assertEquals("+*   ", FormattableUtils.append("foo", createFormatter(), LEFT_JUSTIFY, 5, 2, "+*").toString());
     }
 
     @Test
     public void testIllegalEllipsis() {
-        assertThatIllegalArgumentException().isThrownBy(() -> FormattableUtils.append("foo", createFormatter(), 0, -1, 1, "xx"));
+        assertThrowsExactly(IllegalArgumentException.class, () -> FormattableUtils.append("foo", createFormatter(), 0, -1, 1, "xx"));
     }
 
     @Test
     public void testIllegalEllipsisWith7Args() {
         final String ellipsis = "xxxx";
         final int precisionLessThanEllipsisLength = ellipsis.length() - 1;
-        assertThatIllegalArgumentException()
-                .isThrownBy(() -> FormattableUtils.append("foo", createFormatter(), 0, 0, precisionLessThanEllipsisLength, '}', ellipsis));
+        assertThrowsExactly(IllegalArgumentException.class,
+                () -> FormattableUtils.append("foo", createFormatter(), 0, 0, precisionLessThanEllipsisLength, '}', ellipsis));
     }
 
     @Test
@@ -153,8 +152,7 @@ public class FormattableUtilsTest {
     @Test
     public void testSimplestFormat() {
         final Formattable formattable = new SimplestFormattable("foo");
-
-        assertThat(FormattableUtils.toString(formattable)).isEqualTo("foo");
+        assertEquals("foo", FormattableUtils.toString(formattable));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/OssFuzzTest.java b/src/test/java/org/apache/commons/text/OssFuzzTest.java
index 85ee598a..0b4e1a55 100644
Binary files a/src/test/java/org/apache/commons/text/OssFuzzTest.java and b/src/test/java/org/apache/commons/text/OssFuzzTest.java differ
diff --git a/src/test/java/org/apache/commons/text/RandomStringGeneratorTest.java b/src/test/java/org/apache/commons/text/RandomStringGeneratorTest.java
index fa4b7830..8ac267a1 100644
--- a/src/test/java/org/apache/commons/text/RandomStringGeneratorTest.java
+++ b/src/test/java/org/apache/commons/text/RandomStringGeneratorTest.java
@@ -16,12 +16,11 @@
  */
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
-import static org.assertj.core.api.Assertions.assertThatNullPointerException;
-import static org.assertj.core.api.Assertions.fail;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrowsExactly;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import org.apache.commons.text.RandomStringGenerator.Builder;
 import org.junit.jupiter.api.Test;
@@ -41,27 +40,25 @@ public class RandomStringGeneratorTest {
 
     @Test
     public void testBadMaximumCodePoint() {
-        assertThatIllegalArgumentException().isThrownBy(() -> RandomStringGenerator.builder().withinRange(0, Character.MAX_CODE_POINT + 1));
+        assertThrowsExactly(IllegalArgumentException.class, () -> RandomStringGenerator.builder().withinRange(0, Character.MAX_CODE_POINT + 1));
     }
 
     @Test
     public void testBadMinAndMax() {
-        assertThatIllegalArgumentException().isThrownBy(() -> RandomStringGenerator.builder().withinRange(2, 1));
+        assertThrowsExactly(IllegalArgumentException.class, () -> RandomStringGenerator.builder().withinRange(2, 1));
     }
 
     @Test
     public void testBadMinimumCodePoint() {
-        assertThatIllegalArgumentException().isThrownBy(() -> RandomStringGenerator.builder().withinRange(-1, 1));
+        assertThrowsExactly(IllegalArgumentException.class, () -> RandomStringGenerator.builder().withinRange(-1, 1));
     }
 
     @Test
     public void testChangeOfFilter() {
-        final RandomStringGenerator.Builder builder = RandomStringGenerator.builder().withinRange('a', 'z')
-                .filteredBy(A_FILTER);
+        final RandomStringGenerator.Builder builder = RandomStringGenerator.builder().withinRange('a', 'z').filteredBy(A_FILTER);
         final String str = builder.filteredBy(B_FILTER).build().generate(100);
-
         for (final char c : str.toCharArray()) {
-            assertThat(c == 'b').isTrue();
+            assertEquals('b', c);
         }
     }
 
@@ -71,12 +68,13 @@ public class RandomStringGeneratorTest {
         final int maxLength = 3;
         final RandomStringGenerator generator = RandomStringGenerator.builder().build();
         final String str = generator.generate(minLength, maxLength);
-        assertThat(codePointLength(str)).isBetween(0, 3);
+        final int codePointLength = codePointLength(str);
+        assertTrue(codePointLength > 0 && codePointLength < 3);
     }
 
     @Test
     public void testGenerateMinMaxLengthInvalidLength() {
-        assertThatIllegalArgumentException().isThrownBy(() -> {
+        assertThrowsExactly(IllegalArgumentException.class, () -> {
             final RandomStringGenerator generator = RandomStringGenerator.builder().build();
             generator.generate(-1, 0);
         });
@@ -84,7 +82,7 @@ public class RandomStringGeneratorTest {
 
     @Test
     public void testGenerateMinMaxLengthMinGreaterThanMax() {
-        assertThatIllegalArgumentException().isThrownBy(() -> {
+        assertThrowsExactly(IllegalArgumentException.class, () -> {
             final RandomStringGenerator generator = RandomStringGenerator.builder().build();
             generator.generate(1, 0);
         });
@@ -92,28 +90,23 @@ public class RandomStringGeneratorTest {
 
     @Test
     public void testGenerateTakingIntThrowsNullPointerException() {
-        assertThatNullPointerException().isThrownBy(() -> {
+        assertThrowsExactly(NullPointerException.class, () -> {
             final RandomStringGenerator.Builder randomStringGeneratorBuilder = RandomStringGenerator.builder();
             final CharacterPredicate[] characterPredicateArray = new CharacterPredicate[2];
             randomStringGeneratorBuilder.filteredBy(characterPredicateArray);
             final RandomStringGenerator randomStringGenerator = randomStringGeneratorBuilder.build();
-
             randomStringGenerator.generate(18);
         });
     }
 
     @Test
     public void testInvalidLength() {
-        assertThatIllegalArgumentException().isThrownBy(() -> {
-            final RandomStringGenerator generator = RandomStringGenerator.builder().build();
-            generator.generate(-1);
-        });
+        assertThrowsExactly(IllegalArgumentException.class, () -> RandomStringGenerator.builder().build().generate(-1));
     }
 
     @Test
     public void testMultipleFilters() {
-        final String str = RandomStringGenerator.builder().withinRange('a', 'd')
-                .filteredBy(A_FILTER, B_FILTER).build().generate(5000);
+        final String str = RandomStringGenerator.builder().withinRange('a', 'd').filteredBy(A_FILTER, B_FILTER).build().generate(5000);
 
         boolean aFound = false;
         boolean bFound = false;
@@ -128,7 +121,7 @@ public class RandomStringGeneratorTest {
             }
         }
 
-        assertThat(aFound && bFound).isTrue();
+        assertTrue(aFound && bFound);
     }
 
     @Test
@@ -141,16 +134,16 @@ public class RandomStringGeneratorTest {
             final char c = str.charAt(i);
 
             if (Character.isLowSurrogate(c)) {
-                assertThat(Character.isHighSurrogate(lastChar)).isTrue();
+                assertTrue(Character.isHighSurrogate(lastChar));
             }
 
             if (Character.isHighSurrogate(lastChar)) {
-                assertThat(Character.isLowSurrogate(c)).isTrue();
+                assertTrue(Character.isLowSurrogate(c));
             }
 
             if (Character.isHighSurrogate(c)) {
                 // test this isn't the last character in the string
-                assertThat(i + 1 < str.length()).isTrue();
+                assertTrue(i + 1 < str.length());
             }
 
             lastChar = c;
@@ -163,21 +156,20 @@ public class RandomStringGeneratorTest {
 
         // Request a string in an area of the Basic Multilingual Plane that is
         // largely occupied by private characters
-        final String str = RandomStringGenerator.builder().withinRange(startOfPrivateBMPChars,
-                Character.MIN_SUPPLEMENTARY_CODE_POINT - 1).build().generate(5000);
+        final String str = RandomStringGenerator.builder().withinRange(startOfPrivateBMPChars, Character.MIN_SUPPLEMENTARY_CODE_POINT - 1).build()
+                .generate(5000);
 
         int i = 0;
         do {
             final int codePoint = str.codePointAt(i);
-            assertThat(Character.getType(codePoint) == Character.PRIVATE_USE).isFalse();
+            assertFalse(Character.getType(codePoint) == Character.PRIVATE_USE);
             i += Character.charCount(codePoint);
         } while (i < str.length());
     }
 
     @Test
     public void testRemoveFilters() {
-        final RandomStringGenerator.Builder builder = RandomStringGenerator.builder().withinRange('a', 'z')
-                .filteredBy(A_FILTER);
+        final RandomStringGenerator.Builder builder = RandomStringGenerator.builder().withinRange('a', 'z').filteredBy(A_FILTER);
 
         builder.filteredBy();
 
@@ -201,7 +193,7 @@ public class RandomStringGeneratorTest {
         final String randomText = generator.generate(5);
 
         for (final char c : randomText.toCharArray()) {
-            assertThat(str.indexOf(c) != -1).isTrue();
+            assertTrue(str.indexOf(c) != -1);
         }
     }
 
@@ -211,7 +203,7 @@ public class RandomStringGeneratorTest {
         final RandomStringGenerator generator = RandomStringGenerator.builder().selectFrom('a', 'b', 'c').build();
         final String randomText = generator.generate(5);
         for (final char c : randomText.toCharArray()) {
-            assertThat(str.indexOf(c) != -1).isTrue();
+            assertTrue(str.indexOf(c) != -1);
         }
     }
 
@@ -230,7 +222,7 @@ public class RandomStringGeneratorTest {
         // @formatter:on
         final String randomText = generator.generate(10);
         for (final char c : randomText.toCharArray()) {
-            assertThat(str.indexOf(c) != -1).isTrue();
+            assertTrue(str.indexOf(c) != -1);
         }
     }
 
@@ -257,7 +249,7 @@ public class RandomStringGeneratorTest {
         final int length = 5;
         RandomStringGenerator generator = RandomStringGenerator.builder().selectFrom(null).build();
         String randomText = generator.generate(length);
-        assertThat(codePointLength(randomText)).isEqualTo(length);
+        assertEquals(length, codePointLength(randomText));
         for (final char c : randomText.toCharArray()) {
             assertTrue(c >= Character.MIN_CODE_POINT && c <= Character.MAX_CODE_POINT);
         }
@@ -271,7 +263,7 @@ public class RandomStringGeneratorTest {
         // null input resets
         generator = builder.selectFrom(null).build();
         randomText = generator.generate(length);
-        assertThat(codePointLength(randomText)).isEqualTo(length);
+        assertEquals(length, codePointLength(randomText));
         for (final char c : randomText.toCharArray()) {
             assertTrue(c >= Character.MIN_CODE_POINT && c <= Character.MAX_CODE_POINT);
         }
@@ -282,7 +274,7 @@ public class RandomStringGeneratorTest {
         final int length = 99;
         final RandomStringGenerator generator = RandomStringGenerator.builder().build();
         final String str = generator.generate(length);
-        assertThat(codePointLength(str)).isEqualTo(length);
+        assertEquals(length, codePointLength(str));
     }
 
     @Test
@@ -292,14 +284,14 @@ public class RandomStringGeneratorTest {
 
         final String str = RandomStringGenerator.builder().usingRandom(testRandom).build().generate(10);
         for (final char c : str.toCharArray()) {
-            assertThat(c).isEqualTo(testChar);
+            assertEquals(testChar, c);
         }
     }
 
     @Test
     public void testWithinMultipleRanges() {
         final int length = 5000;
-        final char[][] pairs = {{'a', 'z'}, {'0', '9'}};
+        final char[][] pairs = { { 'a', 'z' }, { '0', '9' } };
         // @formatter:off
         final RandomStringGenerator generator = RandomStringGenerator.builder()
                 .withinRange()
@@ -319,7 +311,7 @@ public class RandomStringGeneratorTest {
         int i = 0;
         do {
             final int codePoint = str.codePointAt(i);
-            assertThat(codePoint >= minimumCodePoint && codePoint <= maximumCodePoint).isTrue();
+            assertTrue(codePoint >= minimumCodePoint && codePoint <= maximumCodePoint);
             i += Character.charCount(codePoint);
         } while (i < str.length());
     }
@@ -329,14 +321,13 @@ public class RandomStringGeneratorTest {
         final int length = 5000;
         final int minimumCodePoint = 'a';
         final int maximumCodePoint = 'z';
-        final RandomStringGenerator generator = RandomStringGenerator.builder()
-                .withinRange(minimumCodePoint, maximumCodePoint).build();
+        final RandomStringGenerator generator = RandomStringGenerator.builder().withinRange(minimumCodePoint, maximumCodePoint).build();
         final String str = generator.generate(length);
 
         int i = 0;
         do {
             final int codePoint = str.codePointAt(i);
-            assertThat(codePoint >= minimumCodePoint && codePoint <= maximumCodePoint).isTrue();
+            assertTrue(codePoint >= minimumCodePoint && codePoint <= maximumCodePoint);
             i += Character.charCount(codePoint);
         } while (i < str.length());
     }
@@ -344,6 +335,6 @@ public class RandomStringGeneratorTest {
     @Test
     public void testZeroLength() {
         final RandomStringGenerator generator = RandomStringGenerator.builder().build();
-        assertThat(generator.generate(0)).isEqualTo("");
+        assertEquals("", generator.generate(0));
     }
 }
diff --git a/src/test/java/org/apache/commons/text/StrBuilderAppendInsertTest.java b/src/test/java/org/apache/commons/text/StrBuilderAppendInsertTest.java
index 5652f576..b826f16c 100644
--- a/src/test/java/org/apache/commons/text/StrBuilderAppendInsertTest.java
+++ b/src/test/java/org/apache/commons/text/StrBuilderAppendInsertTest.java
@@ -17,9 +17,9 @@
 
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.fail;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import java.text.DecimalFormatSymbols;
 import java.util.Arrays;
@@ -53,86 +53,86 @@ public class StrBuilderAppendInsertTest {
     public void testAppend_Boolean() {
         final StrBuilder sb = new StrBuilder();
         sb.append(true);
-        assertThat(sb.toString()).isEqualTo("true");
+        assertEquals("true", sb.toString());
 
         sb.append(false);
-        assertThat(sb.toString()).isEqualTo("truefalse");
+        assertEquals("truefalse", sb.toString());
 
         sb.append('!');
-        assertThat(sb.toString()).isEqualTo("truefalse!");
+        assertEquals("truefalse!", sb.toString());
     }
 
     @Test
     public void testAppend_CharArray() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((char[]) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append(ArrayUtils.EMPTY_CHAR_ARRAY);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
-        sb.append(new char[]{'f', 'o', 'o'});
-        assertThat(sb.toString()).isEqualTo("foo");
+        sb.append(new char[] { 'f', 'o', 'o' });
+        assertEquals("foo", sb.toString());
     }
 
     @Test
     public void testAppend_CharArray_int_int() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((char[]) null, 0, 1);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
-        sb.append(new char[]{'f', 'o', 'o'}, 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        sb.append(new char[] { 'f', 'o', 'o' }, 0, 3);
+        assertEquals("foo", sb.toString());
 
         try {
-            sb.append(new char[]{'b', 'a', 'r'}, -1, 1);
+            sb.append(new char[] { 'b', 'a', 'r' }, -1, 1);
             fail("append(char[], -1,) expected IndexOutOfBoundsException");
         } catch (final IndexOutOfBoundsException e) {
             // expected
         }
 
         try {
-            sb.append(new char[]{'b', 'a', 'r'}, 3, 1);
+            sb.append(new char[] { 'b', 'a', 'r' }, 3, 1);
             fail("append(char[], 3,) expected IndexOutOfBoundsException");
         } catch (final IndexOutOfBoundsException e) {
             // expected
         }
 
         try {
-            sb.append(new char[]{'b', 'a', 'r'}, 1, -1);
+            sb.append(new char[] { 'b', 'a', 'r' }, 1, -1);
             fail("append(char[],, -1) expected IndexOutOfBoundsException");
         } catch (final IndexOutOfBoundsException e) {
             // expected
         }
 
         try {
-            sb.append(new char[]{'b', 'a', 'r'}, 1, 3);
+            sb.append(new char[] { 'b', 'a', 'r' }, 1, 3);
             fail("append(char[], 1, 3) expected IndexOutOfBoundsException");
         } catch (final IndexOutOfBoundsException e) {
             // expected
         }
 
         try {
-            sb.append(new char[]{'b', 'a', 'r'}, -1, 3);
+            sb.append(new char[] { 'b', 'a', 'r' }, -1, 3);
             fail("append(char[], -1, 3) expected IndexOutOfBoundsException");
         } catch (final IndexOutOfBoundsException e) {
             // expected
         }
 
         try {
-            sb.append(new char[]{'b', 'a', 'r'}, 4, 0);
+            sb.append(new char[] { 'b', 'a', 'r' }, 4, 0);
             fail("append(char[], 4, 0) expected IndexOutOfBoundsException");
         } catch (final IndexOutOfBoundsException e) {
             // expected
         }
 
-        sb.append(new char[]{'b', 'a', 'r'}, 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        sb.append(new char[] { 'b', 'a', 'r' }, 3, 0);
+        assertEquals("foo", sb.toString());
 
-        sb.append(new char[]{'a', 'b', 'c', 'b', 'a', 'r', 'd', 'e', 'f'}, 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        sb.append(new char[] { 'a', 'b', 'c', 'b', 'a', 'r', 'd', 'e', 'f' }, 3, 3);
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
@@ -141,94 +141,94 @@ public class StrBuilderAppendInsertTest {
 
         sb = new StrBuilder();
         sb.append("Hi", (Object[]) null);
-        assertThat(sb.toString()).isEqualTo("Hi");
+        assertEquals("Hi", sb.toString());
 
         sb = new StrBuilder();
         sb.append("Hi", "Alice");
-        assertThat(sb.toString()).isEqualTo("Hi");
+        assertEquals("Hi", sb.toString());
 
         sb = new StrBuilder();
         sb.append("Hi %s", "Alice");
-        assertThat(sb.toString()).isEqualTo("Hi Alice");
+        assertEquals("Hi Alice", sb.toString());
 
         sb = new StrBuilder();
         sb.append("Hi %s %,d", "Alice", 5000);
         // group separator depends on system locale
         final char groupingSeparator = DecimalFormatSymbols.getInstance().getGroupingSeparator();
         final String expected = "Hi Alice 5" + groupingSeparator + "000";
-        assertThat(sb.toString()).isEqualTo(expected);
+        assertEquals(expected, sb.toString());
     }
 
     @Test
     public void testAppend_Object() {
         final StrBuilder sb = new StrBuilder();
         sb.appendNull();
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.append((Object) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.append(FOO);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append((StringBuffer) null);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer("baz"));
-        assertThat(sb.toString()).isEqualTo("foobaz");
+        assertEquals("foobaz", sb.toString());
 
         sb.append(new StrBuilder("yes"));
-        assertThat(sb.toString()).isEqualTo("foobazyes");
+        assertEquals("foobazyes", sb.toString());
 
         sb.append((CharSequence) "Seq");
-        assertThat(sb.toString()).isEqualTo("foobazyesSeq");
+        assertEquals("foobazyesSeq", sb.toString());
 
         sb.append(new StringBuilder("bld")); // Check it supports StringBuilder
-        assertThat(sb.toString()).isEqualTo("foobazyesSeqbld");
+        assertEquals("foobazyesSeqbld", sb.toString());
     }
 
     @Test
     public void testAppend_PrimitiveNumber() {
         final StrBuilder sb = new StrBuilder();
         sb.append(0);
-        assertThat(sb.toString()).isEqualTo("0");
+        assertEquals("0", sb.toString());
 
         sb.append(1L);
-        assertThat(sb.toString()).isEqualTo("01");
+        assertEquals("01", sb.toString());
 
         sb.append(2.3f);
-        assertThat(sb.toString()).isEqualTo("012.3");
+        assertEquals("012.3", sb.toString());
 
         sb.append(4.5d);
-        assertThat(sb.toString()).isEqualTo("012.34.5");
+        assertEquals("012.34.5", sb.toString());
     }
 
     @Test
     public void testAppend_StrBuilder() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((StrBuilder) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append(new StrBuilder("foo"));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StrBuilder(""));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StrBuilder("bar"));
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_StrBuilder_int_int() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((StrBuilder) null, 0, 1);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append(new StrBuilder("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         try {
             sb.append(new StrBuilder("bar"), -1, 1);
@@ -273,38 +273,38 @@ public class StrBuilderAppendInsertTest {
         }
 
         sb.append(new StrBuilder("bar"), 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StrBuilder("abcbardef"), 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_String() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((String) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append("");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append("bar");
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_String_int_int() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((String) null, 0, 1);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append("foo", 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         try {
             sb.append("bar", -1, 1);
@@ -349,41 +349,41 @@ public class StrBuilderAppendInsertTest {
         }
 
         sb.append("bar", 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append("abcbardef", 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
 
         sb.append((CharSequence) "abcbardef", 4, 3);
-        assertThat(sb.toString()).isEqualTo("foobarard");
+        assertEquals("foobarard", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuffer() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((StringBuffer) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append(new StringBuffer("foo"));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer(""));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer("bar"));
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuffer_int_int() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((StringBuffer) null, 0, 1);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append(new StringBuffer("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         try {
             sb.append(new StringBuffer("bar"), -1, 1);
@@ -428,38 +428,38 @@ public class StrBuilderAppendInsertTest {
         }
 
         sb.append(new StringBuffer("bar"), 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer("abcbardef"), 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuilder() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((String) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append(new StringBuilder("foo"));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuilder(""));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuilder("bar"));
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuilder_int_int() {
         StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL").append((String) null, 0, 1);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new StrBuilder();
         sb.append(new StringBuilder("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         try {
             sb.append(new StringBuilder("bar"), -1, 1);
@@ -504,215 +504,215 @@ public class StrBuilderAppendInsertTest {
         }
 
         sb.append(new StringBuilder("bar"), 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuilder("abcbardef"), 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
 
         sb.append(new StringBuilder("abcbardef"), 4, 3);
-        assertThat(sb.toString()).isEqualTo("foobarard");
+        assertEquals("foobarard", sb.toString());
     }
 
     @Test
     public void testAppendAll_Array() {
         final StrBuilder sb = new StrBuilder();
         sb.appendAll((Object[]) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll();
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll("foo", "bar", "baz");
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.appendAll("foo", "bar", "baz");
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
     }
 
     @Test
     public void testAppendAll_Collection() {
         final StrBuilder sb = new StrBuilder();
         sb.appendAll((Collection<?>) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Collections.EMPTY_LIST);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Arrays.asList("foo", "bar", "baz"));
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
     }
 
     @Test
     public void testAppendAll_Iterator() {
         final StrBuilder sb = new StrBuilder();
         sb.appendAll((Iterator<?>) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Collections.EMPTY_LIST.iterator());
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Arrays.asList("foo", "bar", "baz").iterator());
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadLeft() {
         final StrBuilder sb = new StrBuilder();
         sb.appendFixedWidthPadLeft("foo", -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 1, '-');
-        assertThat(sb.toString()).isEqualTo("o");
+        assertEquals("o", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 2, '-');
-        assertThat(sb.toString()).isEqualTo("oo");
+        assertEquals("oo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 3, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 4, '-');
-        assertThat(sb.toString()).isEqualTo("-foo");
+        assertEquals("-foo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
-        //            1234567890
-        assertThat(sb.toString()).isEqualTo("-------foo");
+        assertEquals(10, sb.length());
+        // 1234567890
+        assertEquals("-------foo", sb.toString());
 
         sb.clear();
         sb.setNullText("null");
         sb.appendFixedWidthPadLeft(null, 5, '-');
-        assertThat(sb.toString()).isEqualTo("-null");
+        assertEquals("-null", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadLeft_int() {
         final StrBuilder sb = new StrBuilder();
         sb.appendFixedWidthPadLeft(123, -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 1, '-');
-        assertThat(sb.toString()).isEqualTo("3");
+        assertEquals("3", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 2, '-');
-        assertThat(sb.toString()).isEqualTo("23");
+        assertEquals("23", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 3, '-');
-        assertThat(sb.toString()).isEqualTo("123");
+        assertEquals("123", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 4, '-');
-        assertThat(sb.toString()).isEqualTo("-123");
+        assertEquals("-123", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
-        //            1234567890
-        assertThat(sb.toString()).isEqualTo("-------123");
+        assertEquals(10, sb.length());
+        // 1234567890
+        assertEquals("-------123", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadRight() {
         final StrBuilder sb = new StrBuilder();
         sb.appendFixedWidthPadRight("foo", -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 1, '-');
-        assertThat(sb.toString()).isEqualTo("f");
+        assertEquals("f", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 2, '-');
-        assertThat(sb.toString()).isEqualTo("fo");
+        assertEquals("fo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 3, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 4, '-');
-        assertThat(sb.toString()).isEqualTo("foo-");
+        assertEquals("foo-", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
-        //            1234567890
-        assertThat(sb.toString()).isEqualTo("foo-------");
+        assertEquals(10, sb.length());
+        // 1234567890
+        assertEquals("foo-------", sb.toString());
 
         sb.clear();
         sb.setNullText("null");
         sb.appendFixedWidthPadRight(null, 5, '-');
-        assertThat(sb.toString()).isEqualTo("null-");
+        assertEquals("null-", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadRight_int() {
         final StrBuilder sb = new StrBuilder();
         sb.appendFixedWidthPadRight(123, -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 1, '-');
-        assertThat(sb.toString()).isEqualTo("1");
+        assertEquals("1", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 2, '-');
-        assertThat(sb.toString()).isEqualTo("12");
+        assertEquals("12", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 3, '-');
-        assertThat(sb.toString()).isEqualTo("123");
+        assertEquals("123", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 4, '-');
-        assertThat(sb.toString()).isEqualTo("123-");
+        assertEquals("123-", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
-        //            1234567890
-        assertThat(sb.toString()).isEqualTo("123-------");
+        assertEquals(10, sb.length());
+        // 1234567890
+        assertEquals("123-------", sb.toString());
     }
 
     @Test
     public void testAppendln_Boolean() {
         final StrBuilder sb = new StrBuilder();
         sb.appendln(true);
-        assertThat(sb.toString()).isEqualTo("true" + SEP);
+        assertEquals("true" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(false);
-        assertThat(sb.toString()).isEqualTo("false" + SEP);
+        assertEquals("false" + SEP, sb.toString());
     }
 
     @Test
@@ -726,6 +726,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -733,9 +734,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln("foo".toCharArray());
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -749,6 +750,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str, startIndex, length);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -756,9 +758,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln("foo".toCharArray(), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -772,6 +774,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -779,41 +782,41 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln("Hello %s", "Alice");
-        assertThat(sb.toString()).isEqualTo("Hello Alice" + SEP);
-        assertThat(count[0]).isEqualTo(2); // appendNewLine() calls append(String)
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("Hello Alice" + SEP, sb.toString());
+        assertEquals(2, count[0]); // appendNewLine() calls append(String)
+        assertEquals(1, count[1]);
     }
 
     @Test
     public void testAppendln_Object() {
         final StrBuilder sb = new StrBuilder();
         sb.appendln((Object) null);
-        assertThat(sb.toString()).isEqualTo("" + SEP);
+        assertEquals("" + SEP, sb.toString());
 
         sb.appendln(FOO);
-        assertThat(sb.toString()).isEqualTo(SEP + "foo" + SEP);
+        assertEquals(SEP + "foo" + SEP, sb.toString());
 
         sb.appendln(Integer.valueOf(6));
-        assertThat(sb.toString()).isEqualTo(SEP + "foo" + SEP + "6" + SEP);
+        assertEquals(SEP + "foo" + SEP + "6" + SEP, sb.toString());
     }
 
     @Test
     public void testAppendln_PrimitiveNumber() {
         final StrBuilder sb = new StrBuilder();
         sb.appendln(0);
-        assertThat(sb.toString()).isEqualTo("0" + SEP);
+        assertEquals("0" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(1L);
-        assertThat(sb.toString()).isEqualTo("1" + SEP);
+        assertEquals("1" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(2.3f);
-        assertThat(sb.toString()).isEqualTo("2.3" + SEP);
+        assertEquals("2.3" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(4.5d);
-        assertThat(sb.toString()).isEqualTo("4.5" + SEP);
+        assertEquals("4.5" + SEP, sb.toString());
     }
 
     @Test
@@ -827,6 +830,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -834,9 +838,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln(new StrBuilder("foo"));
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -850,6 +854,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str, startIndex, length);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -857,9 +862,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln(new StrBuilder("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -873,6 +878,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -880,9 +886,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln("foo");
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(2); // appendNewLine() calls append(String)
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(2, count[0]); // appendNewLine() calls append(String)
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -896,6 +902,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str, startIndex, length);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -903,9 +910,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln("foo", 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -919,6 +926,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -926,9 +934,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln(new StringBuffer("foo"));
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -942,6 +950,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str, startIndex, length);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -949,9 +958,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln(new StringBuffer("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -965,6 +974,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -972,9 +982,9 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln(new StringBuilder("foo"));
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
@@ -988,6 +998,7 @@ public class StrBuilderAppendInsertTest {
                 count[0]++;
                 return super.append(str, startIndex, length);
             }
+
             @Override
             public StrBuilder appendNewLine() {
                 count[1]++;
@@ -995,52 +1006,52 @@ public class StrBuilderAppendInsertTest {
             }
         };
         sb.appendln(new StringBuilder("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
-        assertThat(count[0]).isEqualTo(1);
-        assertThat(count[1]).isEqualTo(1);
+        assertEquals("foo" + SEP, sb.toString());
+        assertEquals(1, count[0]);
+        assertEquals(1, count[1]);
     }
 
     @Test
     public void testAppendNewLine() {
         StrBuilder sb = new StrBuilder("---");
         sb.appendNewLine().append("+++");
-        assertThat(sb.toString()).isEqualTo("---" + SEP + "+++");
+        assertEquals("---" + SEP + "+++", sb.toString());
 
         sb = new StrBuilder("---");
         sb.setNewLineText("#").appendNewLine().setNewLineText(null).appendNewLine();
-        assertThat(sb.toString()).isEqualTo("---#" + SEP);
+        assertEquals("---#" + SEP, sb.toString());
     }
 
     @Test
     public void testAppendPadding() {
         final StrBuilder sb = new StrBuilder();
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.appendPadding(-1, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.appendPadding(0, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.appendPadding(1, '-');
-        assertThat(sb.toString()).isEqualTo("foo-");
+        assertEquals("foo-", sb.toString());
 
         sb.appendPadding(16, '-');
-        assertThat(sb.length()).isEqualTo(20);
-        //            12345678901234567890
-        assertThat(sb.toString()).isEqualTo("foo-----------------");
+        assertEquals(20, sb.length());
+        // 12345678901234567890
+        assertEquals("foo-----------------", sb.toString());
     }
 
     @Test
     public void testAppendSeparator_char() {
         final StrBuilder sb = new StrBuilder();
-        sb.appendSeparator(',');  // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        sb.appendSeparator(','); // no effect
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(',');
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
@@ -1049,51 +1060,51 @@ public class StrBuilderAppendInsertTest {
         final char startSeparator = ':';
         final char standardSeparator = ',';
         final String foo = "foo";
-        sb.appendSeparator(standardSeparator, startSeparator);  // no effect
-        assertThat(sb.toString()).isEqualTo(String.valueOf(startSeparator));
+        sb.appendSeparator(standardSeparator, startSeparator); // no effect
+        assertEquals(String.valueOf(startSeparator), sb.toString());
         sb.append(foo);
-        assertThat(sb.toString()).isEqualTo(String.valueOf(startSeparator) + foo);
+        assertEquals(String.valueOf(startSeparator) + foo, sb.toString());
         sb.appendSeparator(standardSeparator, startSeparator);
-        assertThat(sb.toString()).isEqualTo(String.valueOf(startSeparator) + foo + standardSeparator);
+        assertEquals(String.valueOf(startSeparator) + foo + standardSeparator, sb.toString());
     }
 
     @Test
     public void testAppendSeparator_char_int() {
         final StrBuilder sb = new StrBuilder();
-        sb.appendSeparator(',', 0);  // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        sb.appendSeparator(',', 0); // no effect
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(',', 1);
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
 
-        sb.appendSeparator(',', -1);  // no effect
-        assertThat(sb.toString()).isEqualTo("foo,");
+        sb.appendSeparator(',', -1); // no effect
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
     public void testAppendSeparator_String() {
         final StrBuilder sb = new StrBuilder();
-        sb.appendSeparator(",");  // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        sb.appendSeparator(","); // no effect
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(",");
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
     public void testAppendSeparator_String_int() {
         final StrBuilder sb = new StrBuilder();
-        sb.appendSeparator(",", 0);  // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        sb.appendSeparator(",", 0); // no effect
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(",", 1);
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
 
-        sb.appendSeparator(",", -1);  // no effect
-        assertThat(sb.toString()).isEqualTo("foo,");
+        sb.appendSeparator(",", -1); // no effect
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
@@ -1103,130 +1114,131 @@ public class StrBuilderAppendInsertTest {
         final String standardSeparator = ",";
         final String foo = "foo";
         sb.appendSeparator(null, null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(standardSeparator, null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(standardSeparator, startSeparator);
-        assertThat(sb.toString()).isEqualTo(startSeparator);
+        assertEquals(startSeparator, sb.toString());
         sb.appendSeparator(null, null);
-        assertThat(sb.toString()).isEqualTo(startSeparator);
+        assertEquals(startSeparator, sb.toString());
         sb.appendSeparator(null, startSeparator);
-        assertThat(sb.toString()).isEqualTo(startSeparator);
+        assertEquals(startSeparator, sb.toString());
         sb.append(foo);
-        assertThat(sb.toString()).isEqualTo(startSeparator + foo);
+        assertEquals(startSeparator + foo, sb.toString());
         sb.appendSeparator(standardSeparator, startSeparator);
-        assertThat(sb.toString()).isEqualTo(startSeparator + foo + standardSeparator);
+        assertEquals(startSeparator + foo + standardSeparator, sb.toString());
     }
 
     @Test
     public void testAppendWithNullText() {
         final StrBuilder sb = new StrBuilder();
         sb.setNullText("NULL");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.appendNull();
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb.append((Object) null);
-        assertThat(sb.toString()).isEqualTo("NULLNULL");
+        assertEquals("NULLNULL", sb.toString());
 
         sb.append(FOO);
-        assertThat(sb.toString()).isEqualTo("NULLNULLfoo");
+        assertEquals("NULLNULLfoo", sb.toString());
 
         sb.append((String) null);
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULL");
+        assertEquals("NULLNULLfooNULL", sb.toString());
 
         sb.append("");
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULL");
+        assertEquals("NULLNULLfooNULL", sb.toString());
 
         sb.append("bar");
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULLbar");
+        assertEquals("NULLNULLfooNULLbar", sb.toString());
 
         sb.append((StringBuffer) null);
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULLbarNULL");
+        assertEquals("NULLNULLfooNULLbarNULL", sb.toString());
 
         sb.append(new StringBuffer("baz"));
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULLbarNULLbaz");
+        assertEquals("NULLNULLfooNULLbarNULLbaz", sb.toString());
     }
 
     @Test
     public void testAppendWithSeparators_Array() {
         final StrBuilder sb = new StrBuilder();
         sb.appendWithSeparators((Object[]) null, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(ArrayUtils.EMPTY_OBJECT_ARRAY, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
-        sb.appendWithSeparators(new Object[]{"foo", "bar", "baz"}, ",");
-        assertThat(sb.toString()).isEqualTo("foo,bar,baz");
+        sb.appendWithSeparators(new Object[] { "foo", "bar", "baz" }, ",");
+        assertEquals("foo,bar,baz", sb.toString());
 
         sb.clear();
-        sb.appendWithSeparators(new Object[]{"foo", "bar", "baz"}, null);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        sb.appendWithSeparators(new Object[] { "foo", "bar", "baz" }, null);
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
-        sb.appendWithSeparators(new Object[]{"foo", null, "baz"}, ",");
-        assertThat(sb.toString()).isEqualTo("foo,,baz");
+        sb.appendWithSeparators(new Object[] { "foo", null, "baz" }, ",");
+        assertEquals("foo,,baz", sb.toString());
     }
 
     @Test
     public void testAppendWithSeparators_Collection() {
         final StrBuilder sb = new StrBuilder();
         sb.appendWithSeparators((Collection<?>) null, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Collections.EMPTY_LIST, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz"), ",");
-        assertThat(sb.toString()).isEqualTo("foo,bar,baz");
+        assertEquals("foo,bar,baz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz"), null);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", null, "baz"), ",");
-        assertThat(sb.toString()).isEqualTo("foo,,baz");
+        assertEquals("foo,,baz", sb.toString());
     }
+
     @Test
     public void testAppendWithSeparators_Iterator() {
         final StrBuilder sb = new StrBuilder();
         sb.appendWithSeparators((Iterator<?>) null, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Collections.EMPTY_LIST.iterator(), ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz").iterator(), ",");
-        assertThat(sb.toString()).isEqualTo("foo,bar,baz");
+        assertEquals("foo,bar,baz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz").iterator(), null);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", null, "baz").iterator(), ",");
-        assertThat(sb.toString()).isEqualTo("foo,,baz");
+        assertEquals("foo,,baz", sb.toString());
     }
 
     @Test
     public void testAppendWithSeparatorsWithNullText() {
         final StrBuilder sb = new StrBuilder();
         sb.setNullText("null");
-        sb.appendWithSeparators(new Object[]{"foo", null, "baz"}, ",");
-        assertThat(sb.toString()).isEqualTo("foo,null,baz");
+        sb.appendWithSeparators(new Object[] { "foo", null, "baz" }, ",");
+        assertEquals("foo,null,baz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", null, "baz"), ",");
-        assertThat(sb.toString()).isEqualTo("foo,null,baz");
+        assertEquals("foo,null,baz", sb.toString());
     }
 
     @Test
@@ -1234,151 +1246,145 @@ public class StrBuilderAppendInsertTest {
 
         final StrBuilder sb = new StrBuilder();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, FOO));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, FOO));
 
         sb.insert(0, (Object) null);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, FOO);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, "foo"));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, "foo"));
 
         sb.insert(0, (String) null);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, "foo");
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
-        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, new char[]{'f', 'o', 'o'}));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, new char[] { 'f', 'o', 'o' }));
 
-        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, new char[]{'f', 'o', 'o'}));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, new char[] { 'f', 'o', 'o' }));
 
         sb.insert(0, (char[]) null);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, ArrayUtils.EMPTY_CHAR_ARRAY);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
-        sb.insert(0, new char[]{'f', 'o', 'o'});
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        sb.insert(0, new char[] { 'f', 'o', 'o' });
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
-        assertThrows(IndexOutOfBoundsException.class,
-                () -> sb.insert(-1, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 3, 3));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, 3, 3));
 
-        assertThrows(IndexOutOfBoundsException.class,
-                () -> sb.insert(7, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 3, 3));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, 3, 3));
 
         sb.insert(0, (char[]) null, 0, 0);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, ArrayUtils.EMPTY_CHAR_ARRAY, 0, 0);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
-        assertThrows(IndexOutOfBoundsException.class,
-                () -> sb.insert(0, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, -1, 3));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(0, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, -1, 3));
 
-        assertThrows(IndexOutOfBoundsException.class,
-                () -> sb.insert(0, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 10, 3));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(0, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, 10, 3));
 
-        assertThrows(IndexOutOfBoundsException.class,
-                () -> sb.insert(0, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 0, -1));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(0, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, 0, -1));
 
-        assertThrows(IndexOutOfBoundsException.class,
-                () -> sb.insert(0, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 0, 10));
+        assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(0, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, 0, 10));
 
-        sb.insert(0, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 0, 0);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        sb.insert(0, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, 0, 0);
+        assertEquals("barbaz", sb.toString());
 
-        sb.insert(0, new char[]{'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        sb.insert(0, new char[] { 'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f' }, 3, 3);
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, true));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, true));
 
         sb.insert(0, true);
-        assertThat(sb.toString()).isEqualTo("truebarbaz");
+        assertEquals("truebarbaz", sb.toString());
 
         sb.insert(0, false);
-        assertThat(sb.toString()).isEqualTo("falsetruebarbaz");
+        assertEquals("falsetruebarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, '!'));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, '!'));
 
         sb.insert(0, '!');
-        assertThat(sb.toString()).isEqualTo("!barbaz");
+        assertEquals("!barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 0));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 0));
 
         sb.insert(0, '0');
-        assertThat(sb.toString()).isEqualTo("0barbaz");
+        assertEquals("0barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 1L));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 1L));
 
         sb.insert(0, 1L);
-        assertThat(sb.toString()).isEqualTo("1barbaz");
+        assertEquals("1barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 2.3F));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 2.3F));
 
         sb.insert(0, 2.3F);
-        assertThat(sb.toString()).isEqualTo("2.3barbaz");
+        assertEquals("2.3barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 4.5D));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 4.5D));
 
         sb.insert(0, 4.5D);
-        assertThat(sb.toString()).isEqualTo("4.5barbaz");
+        assertEquals("4.5barbaz", sb.toString());
     }
 
     @Test
@@ -1386,37 +1392,37 @@ public class StrBuilderAppendInsertTest {
         final StrBuilder sb = new StrBuilder();
         sb.setNullText("null");
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, FOO));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, FOO));
 
         sb.insert(0, (Object) null);
-        assertThat(sb.toString()).isEqualTo("nullbarbaz");
+        assertEquals("nullbarbaz", sb.toString());
 
         sb.insert(0, FOO);
-        assertThat(sb.toString()).isEqualTo("foonullbarbaz");
+        assertEquals("foonullbarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, "foo"));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, "foo"));
 
         sb.insert(0, (String) null);
-        assertThat(sb.toString()).isEqualTo("nullbarbaz");
+        assertEquals("nullbarbaz", sb.toString());
 
         sb.insert(0, "foo");
-        assertThat(sb.toString()).isEqualTo("foonullbarbaz");
+        assertEquals("foonullbarbaz", sb.toString());
 
         sb.insert(0, (char[]) null);
-        assertThat(sb.toString()).isEqualTo("nullfoonullbarbaz");
+        assertEquals("nullfoonullbarbaz", sb.toString());
 
         sb.insert(0, (char[]) null, 0, 0);
-        assertThat(sb.toString()).isEqualTo("nullnullfoonullbarbaz");
+        assertEquals("nullnullfoonullbarbaz", sb.toString());
     }
 
     /** See: https://issues.apache.org/jira/browse/LANG-299 */
@@ -1424,6 +1430,6 @@ public class StrBuilderAppendInsertTest {
     public void testLang299() {
         final StrBuilder sb = new StrBuilder(1);
         sb.appendFixedWidthPadRight("foo", 1, '-');
-        assertThat(sb.toString()).isEqualTo("f");
+        assertEquals("f", sb.toString());
     }
 }
diff --git a/src/test/java/org/apache/commons/text/StrBuilderTest.java b/src/test/java/org/apache/commons/text/StrBuilderTest.java
index 24ee1a02..54799953 100644
--- a/src/test/java/org/apache/commons/text/StrBuilderTest.java
+++ b/src/test/java/org/apache/commons/text/StrBuilderTest.java
@@ -17,8 +17,6 @@
 
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
-import static org.assertj.core.api.Assertions.fail;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -29,6 +27,7 @@ import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import java.io.IOException;
 import java.io.Reader;
@@ -84,7 +83,7 @@ public class StrBuilderTest {
         assertFalse(sb.equals(other));
     }
 
-     @Test
+    @Test
     public void testAppendCharBuffer() {
         final StrBuilder sb1 = new StrBuilder();
         final CharBuffer buf = CharBuffer.allocate(10);
@@ -180,22 +179,20 @@ public class StrBuilderTest {
 
     @Test
     public void testAppendTakingTwoIntsWithIndexOutOfBoundsThrowsStringIndexOutOfBoundsExceptionTwo() {
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(() -> {
+        assertThrows(StringIndexOutOfBoundsException.class, () -> {
             final Charset charset = Charset.defaultCharset();
             final ByteBuffer byteBuffer = charset.encode("asdf");
             final CharBuffer charBuffer = charset.decode(byteBuffer);
-
             new StrBuilder().append(charBuffer, 933, 654);
         });
     }
 
     @Test
     public void testAppendTakingTwoIntsWithZeroThrowsStringIndexOutOfBoundsException() {
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(() -> {
+        assertThrows(StringIndexOutOfBoundsException.class, () -> {
             final Charset charset = Charset.defaultCharset();
             final ByteBuffer byteBuffer = charset.encode("end < start");
             final CharBuffer charBuffer = charset.decode(byteBuffer);
-
             new StrBuilder(630).append(charBuffer, 0, 630);
         });
     }
@@ -233,7 +230,7 @@ public class StrBuilderTest {
         assertEquals("Test 1234567890", builder.toString());
     }
 
-     @Test
+    @Test
     public void testAppendToWriter() throws Exception {
         final StrBuilder sb = new StrBuilder("1234567890");
         final StringWriter writer = new StringWriter();
@@ -250,7 +247,7 @@ public class StrBuilderTest {
         assertEquals(sb.toString(), sb.build());
     }
 
-     @Test
+    @Test
     public void testAsReader() throws Exception {
         final StrBuilder sb = new StrBuilder("some text");
         try (Reader reader = sb.asReader()) {
@@ -333,7 +330,7 @@ public class StrBuilderTest {
         }
     }
 
-     @Test
+    @Test
     public void testAsTokenizer() throws Exception {
         // from Javadoc
         final StrBuilder b = new StrBuilder();
@@ -371,7 +368,7 @@ public class StrBuilderTest {
         assertEquals("a b c d ", t.getContent());
     }
 
-     @Test
+    @Test
     public void testAsWriter() throws Exception {
         final StrBuilder sb = new StrBuilder("base");
         try (Writer writer = sb.asWriter()) {
@@ -379,10 +376,10 @@ public class StrBuilderTest {
             writer.write('l');
             assertEquals("basel", sb.toString());
 
-            writer.write(new char[] {'i', 'n'});
+            writer.write(new char[] { 'i', 'n' });
             assertEquals("baselin", sb.toString());
 
-            writer.write(new char[] {'n', 'e', 'r'}, 1, 2);
+            writer.write(new char[] { 'n', 'e', 'r' }, 1, 2);
             assertEquals("baseliner", sb.toString());
 
             writer.write(" rout");
@@ -406,7 +403,7 @@ public class StrBuilderTest {
         }
     }
 
-     @Test
+    @Test
     public void testCapacity() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(sb.buffer.length, sb.capacity());
@@ -415,7 +412,7 @@ public class StrBuilderTest {
         assertEquals(sb.buffer.length, sb.capacity());
     }
 
-     @Test
+    @Test
     public void testCapacityAndLength() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(32, sb.capacity());
@@ -494,7 +491,7 @@ public class StrBuilderTest {
         assertTrue(sb.isEmpty());
     }
 
-     @Test
+    @Test
     public void testChaining() {
         final StrBuilder sb = new StrBuilder();
         assertSame(sb, sb.setNewLineText(null));
@@ -508,7 +505,7 @@ public class StrBuilderTest {
         assertSame(sb, sb.trim());
     }
 
-     @Test
+    @Test
     public void testCharAt() {
         final StrBuilder sb = new StrBuilder();
         assertThrows(IndexOutOfBoundsException.class, () -> sb.charAt(0));
@@ -530,7 +527,7 @@ public class StrBuilderTest {
         assertTrue(sb.buffer.length >= 5);
     }
 
-     @Test
+    @Test
     public void testConstructors() {
         final StrBuilder sb0 = new StrBuilder();
         assertEquals(32, sb0.capacity());
@@ -573,7 +570,7 @@ public class StrBuilderTest {
         assertEquals(3, sb7.size());
     }
 
-     @Test
+    @Test
     public void testContains_char() {
         final StrBuilder sb = new StrBuilder("abcdefghijklmnopqrstuvwxyz");
         assertTrue(sb.contains('a'));
@@ -607,7 +604,7 @@ public class StrBuilderTest {
         assertTrue(sb.contains(A_NUMBER_MATCHER));
     }
 
-     @Test
+    @Test
     public void testDeleteAll_char() {
         StrBuilder sb = new StrBuilder("abcbccba");
         sb.deleteAll('X');
@@ -624,7 +621,7 @@ public class StrBuilderTest {
         assertEquals("", sb.toString());
     }
 
-     @Test
+    @Test
     public void testDeleteAll_String() {
         StrBuilder sb = new StrBuilder("abcbccba");
         sb.deleteAll((String) null);
@@ -650,7 +647,7 @@ public class StrBuilderTest {
         assertEquals("", sb.toString());
     }
 
-     @Test
+    @Test
     public void testDeleteAll_StrMatcher() {
         StrBuilder sb = new StrBuilder("A0xA1A2yA3");
         sb.deleteAll((StrMatcher) null);
@@ -667,7 +664,7 @@ public class StrBuilderTest {
         assertEquals("", sb.toString());
     }
 
-     @Test
+    @Test
     public void testDeleteCharAt() {
         final StrBuilder sb = new StrBuilder("abc");
         sb.deleteCharAt(0);
@@ -678,7 +675,7 @@ public class StrBuilderTest {
 
     @Test
     public void testDeleteCharAtWithNegative() {
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(() -> new StrBuilder().deleteCharAt(-1258));
+        assertThrows(StringIndexOutOfBoundsException.class, () -> new StrBuilder().deleteCharAt(-1258));
     }
 
     @Test
@@ -741,7 +738,7 @@ public class StrBuilderTest {
         assertEquals("", sb.toString());
     }
 
-     @Test
+    @Test
     public void testDeleteIntInt() {
         final StrBuilder sb = new StrBuilder("abc");
         sb.delete(0, 1);
@@ -790,7 +787,7 @@ public class StrBuilderTest {
         assertTrue(sb.capacity() >= 40);
     }
 
-     @Test
+    @Test
     public void testEquals() {
         final StrBuilder sb1 = new StrBuilder();
         final StrBuilder sb2 = new StrBuilder();
@@ -815,7 +812,7 @@ public class StrBuilderTest {
         assertNotEquals("abc", sb1);
     }
 
-     @Test
+    @Test
     public void testEqualsIgnoreCase() {
         final StrBuilder sb1 = new StrBuilder();
         final StrBuilder sb2 = new StrBuilder();
@@ -850,7 +847,7 @@ public class StrBuilderTest {
         sb.append("junit");
         a = sb.getChars(input);
         assertSame(input, a);
-        assertArrayEquals(new char[] {'j', 'u', 'n', 'i', 't', 0, 0, 0, 0, 0 }, a);
+        assertArrayEquals(new char[] { 'j', 'u', 'n', 'i', 't', 0, 0, 0, 0, 0 }, a);
 
         a = sb.getChars(null);
         assertNotSame(input, a);
@@ -873,11 +870,11 @@ public class StrBuilderTest {
         sb.append("junit");
         char[] a = new char[5];
         sb.getChars(0, 5, a, 0);
-        assertArrayEquals(new char[] {'j', 'u', 'n', 'i', 't' }, a);
+        assertArrayEquals(new char[] { 'j', 'u', 'n', 'i', 't' }, a);
 
         a = new char[5];
         sb.getChars(0, 2, a, 3);
-        assertArrayEquals(new char[] {0, 0, 0, 'j', 'u' }, a);
+        assertArrayEquals(new char[] { 0, 0, 0, 'j', 'u' }, a);
 
         try {
             sb.getChars(-1, 0, a, 0);
@@ -908,7 +905,7 @@ public class StrBuilderTest {
         }
     }
 
-     @Test
+    @Test
     public void testGetSetNewLineText() {
         final StrBuilder sb = new StrBuilder();
         assertNull(sb.getNewLineText());
@@ -923,7 +920,7 @@ public class StrBuilderTest {
         assertNull(sb.getNewLineText());
     }
 
-     @Test
+    @Test
     public void testGetSetNullText() {
         final StrBuilder sb = new StrBuilder();
         assertNull(sb.getNullText());
@@ -941,7 +938,7 @@ public class StrBuilderTest {
         assertNull(sb.getNullText());
     }
 
-     @Test
+    @Test
     public void testHashCode() {
         final StrBuilder sb = new StrBuilder();
         final int hc1a = sb.hashCode();
@@ -956,7 +953,7 @@ public class StrBuilderTest {
         assertEquals(hc2a, hc2b);
     }
 
-     @Test
+    @Test
     public void testIndexOf_char() {
         final StrBuilder sb = new StrBuilder("abab");
         assertEquals(0, sb.indexOf('a'));
@@ -992,7 +989,7 @@ public class StrBuilderTest {
         assertEquals(-1, sb.indexOf('z', 3));
     }
 
-     @Test
+    @Test
     public void testIndexOf_String() {
         final StrBuilder sb = new StrBuilder("abab");
 
@@ -1052,7 +1049,7 @@ public class StrBuilderTest {
         assertEquals(-1, sb.indexOf((String) null, 2));
     }
 
-     @Test
+    @Test
     public void testIndexOf_StrMatcher() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(-1, sb.indexOf((StrMatcher) null));
@@ -1129,14 +1126,14 @@ public class StrBuilderTest {
         assertTrue(sb.isEmpty());
     }
 
-     @Test
+    @Test
     public void testLang294() {
         final StrBuilder sb = new StrBuilder("\n%BLAH%\nDo more stuff\neven more stuff\n%BLAH%\n");
         sb.deleteAll("\n%BLAH%");
         assertEquals("\nDo more stuff\neven more stuff\n", sb.toString());
     }
 
-     @Test
+    @Test
     public void testLang295() {
         final StrBuilder sb = new StrBuilder("onetwothree");
         sb.deleteFirst("three");
@@ -1151,7 +1148,7 @@ public class StrBuilderTest {
         assertEquals("**********", sb.toString(), "Failed to invoke appendFixedWidthPadLeft correctly");
     }
 
-     @Test
+    @Test
     public void testLang412Right() {
         final StrBuilder sb = new StrBuilder();
         sb.appendFixedWidthPadRight(null, 10, '*');
@@ -1324,7 +1321,7 @@ public class StrBuilderTest {
         assertEquals("left right", sb.leftString(15));
     }
 
-     @Test
+    @Test
     public void testLength() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(0, sb.length());
@@ -1333,7 +1330,7 @@ public class StrBuilderTest {
         assertEquals(5, sb.length());
     }
 
-     @Test
+    @Test
     public void testMidString() {
         final StrBuilder sb = new StrBuilder("hello goodbye hello");
         assertEquals("goodbye", sb.midString(6, 7));
@@ -1397,7 +1394,7 @@ public class StrBuilderTest {
         assertEquals("Test 123", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReadFromReader() throws Exception {
         String s = "";
         for (int i = 0; i < 100; ++i) {
@@ -1418,7 +1415,7 @@ public class StrBuilderTest {
         assertEquals("Test 123", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReplace_int_int_String() {
         StrBuilder sb = new StrBuilder("abc");
         sb.replace(0, 1, "d");
@@ -1546,7 +1543,7 @@ public class StrBuilderTest {
         assertEquals("aaxaaaayaa", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReplace_StrMatcher_String_int_int_int_VaryMatcher() {
         StrBuilder sb = new StrBuilder("abcbccba");
         sb.replace((StrMatcher) null, "x", 0, sb.length(), -1);
@@ -1655,7 +1652,7 @@ public class StrBuilderTest {
         assertEquals("aaxaaaayaa", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReplaceAll_char_char() {
         final StrBuilder sb = new StrBuilder("abcbccba");
         sb.replaceAll('x', 'y');
@@ -1670,7 +1667,7 @@ public class StrBuilderTest {
         assertEquals("defeffed", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReplaceAll_String_String() {
         StrBuilder sb = new StrBuilder("abcbccba");
         sb.replaceAll((String) null, null);
@@ -1700,7 +1697,7 @@ public class StrBuilderTest {
         assertEquals("xbxxbx", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReplaceAll_StrMatcher_String() {
         StrBuilder sb = new StrBuilder("abcbccba");
         sb.replaceAll((StrMatcher) null, null);
@@ -1738,7 +1735,7 @@ public class StrBuilderTest {
         assertEquals("Dear 012345678901234567, hello 012345678901234567.", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReplaceFirst_char_char() {
         final StrBuilder sb = new StrBuilder("abcbccba");
         sb.replaceFirst('x', 'y');
@@ -1817,7 +1814,7 @@ public class StrBuilderTest {
         assertEquals("***-A2A3-A4", sb.toString());
     }
 
-     @Test
+    @Test
     public void testReverse() {
         final StrBuilder sb = new StrBuilder();
         assertEquals("", sb.reverse().toString());
@@ -1836,7 +1833,7 @@ public class StrBuilderTest {
         assertEquals("left right", sb.rightString(15));
     }
 
-     @Test
+    @Test
     public void testSetCharAt() {
         final StrBuilder sb = new StrBuilder();
         assertThrows(IndexOutOfBoundsException.class, () -> sb.setCharAt(0, 'f'));
@@ -1863,7 +1860,7 @@ public class StrBuilderTest {
         assertThrows(IndexOutOfBoundsException.class, () -> sb.setLength(-1));
     }
 
-     @Test
+    @Test
     public void testSize() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(0, sb.size());
@@ -1872,7 +1869,7 @@ public class StrBuilderTest {
         assertEquals(5, sb.size());
     }
 
-     @Test
+    @Test
     public void testStartsWith() {
         final StrBuilder sb = new StrBuilder();
         assertFalse(sb.startsWith("a"));
@@ -1885,7 +1882,7 @@ public class StrBuilderTest {
         assertFalse(sb.startsWith("cba"));
     }
 
-     @Test
+    @Test
     public void testSubSequenceIntInt() {
         final StrBuilder sb = new StrBuilder("hello goodbye");
         // Start index is negative
@@ -1935,7 +1932,7 @@ public class StrBuilderTest {
         assertThrows(IndexOutOfBoundsException.class, () -> sb.substring(15, 20));
     }
 
-     @Test
+    @Test
     public void testToCharArray() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(0, sb.toCharArray().length);
@@ -1976,13 +1973,13 @@ public class StrBuilderTest {
         assertThrows(IndexOutOfBoundsException.class, () -> sb.toCharArray(6, 5));
     }
 
-     @Test
+    @Test
     public void testToString() {
         final StrBuilder sb = new StrBuilder("abc");
         assertEquals("abc", sb.toString());
     }
 
-     @Test
+    @Test
     public void testToStringBuffer() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(new StringBuffer().toString(), sb.toStringBuffer().toString());
@@ -1991,7 +1988,7 @@ public class StrBuilderTest {
         assertEquals(new StringBuffer("junit").toString(), sb.toStringBuffer().toString());
     }
 
-     @Test
+    @Test
     public void testToStringBuilder() {
         final StrBuilder sb = new StrBuilder();
         assertEquals(new StringBuilder().toString(), sb.toStringBuilder().toString());
@@ -2000,7 +1997,7 @@ public class StrBuilderTest {
         assertEquals(new StringBuilder("junit").toString(), sb.toStringBuilder().toString());
     }
 
-     @Test
+    @Test
     public void testTrim() {
         final StrBuilder sb = new StrBuilder();
         assertEquals("", sb.reverse().toString());
diff --git a/src/test/java/org/apache/commons/text/StrMatcherTest.java b/src/test/java/org/apache/commons/text/StrMatcherTest.java
index d2398538..f70a8d01 100644
--- a/src/test/java/org/apache/commons/text/StrMatcherTest.java
+++ b/src/test/java/org/apache/commons/text/StrMatcherTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
 
 import org.junit.jupiter.api.Test;
 
@@ -48,57 +48,57 @@ public class StrMatcherTest  {
     @Test
     public void testCharMatcher_char() {
         final StrMatcher matcher = StrMatcher.charMatcher('c');
-        assertThat(matcher.isMatch(BUFFER2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 5)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(BUFFER2, 0));
+        assertEquals(0, matcher.isMatch(BUFFER2, 1));
+        assertEquals(1, matcher.isMatch(BUFFER2, 2));
+        assertEquals(0, matcher.isMatch(BUFFER2, 3));
+        assertEquals(0, matcher.isMatch(BUFFER2, 4));
+        assertEquals(0, matcher.isMatch(BUFFER2, 5));
     }
 
     @Test
     public void testCharSetMatcher_charArray() {
         final StrMatcher matcher = StrMatcher.charSetMatcher("ace".toCharArray());
-        assertThat(matcher.isMatch(BUFFER2, 0)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 4)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER2, 5)).isEqualTo(0);
-        assertThat(StrMatcher.charSetMatcher()).isSameAs(StrMatcher.noneMatcher());
-        assertThat(StrMatcher.charSetMatcher((char[]) null)).isSameAs(StrMatcher.noneMatcher());
+        assertEquals(1, matcher.isMatch(BUFFER2, 0));
+        assertEquals(0, matcher.isMatch(BUFFER2, 1));
+        assertEquals(1, matcher.isMatch(BUFFER2, 2));
+        assertEquals(0, matcher.isMatch(BUFFER2, 3));
+        assertEquals(1, matcher.isMatch(BUFFER2, 4));
+        assertEquals(0, matcher.isMatch(BUFFER2, 5));
+        assertSame(StrMatcher.charSetMatcher(), StrMatcher.noneMatcher());
+        assertSame(StrMatcher.charSetMatcher((char[]) null), StrMatcher.noneMatcher());
         StrMatcherTest.assertStrMatcherImpl("CharMatcher", StrMatcher.charSetMatcher("a".toCharArray()));
     }
 
     @Test
     public void testCharSetMatcher_String() {
         final StrMatcher matcher = StrMatcher.charSetMatcher("ace");
-        assertThat(matcher.isMatch(BUFFER2, 0)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 4)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER2, 5)).isEqualTo(0);
-        assertThat(StrMatcher.charSetMatcher("")).isSameAs(StrMatcher.noneMatcher());
-        assertThat(StrMatcher.charSetMatcher((String) null)).isSameAs(StrMatcher.noneMatcher());
+        assertEquals(1, matcher.isMatch(BUFFER2, 0));
+        assertEquals(0, matcher.isMatch(BUFFER2, 1));
+        assertEquals(1, matcher.isMatch(BUFFER2, 2));
+        assertEquals(0, matcher.isMatch(BUFFER2, 3));
+        assertEquals(1, matcher.isMatch(BUFFER2, 4));
+        assertEquals(0, matcher.isMatch(BUFFER2, 5));
+        assertSame(StrMatcher.charSetMatcher(""), StrMatcher.noneMatcher());
+        assertSame(StrMatcher.charSetMatcher((String) null), StrMatcher.noneMatcher());
         StrMatcherTest.assertStrMatcherImpl("CharMatcher", StrMatcher.charSetMatcher("a"));
     }
 
     @Test
     public void testCommaMatcher() {
         final StrMatcher matcher = StrMatcher.commaMatcher();
-        assertThat(StrMatcher.commaMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 1)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 2)).isEqualTo(0);
+        assertSame(StrMatcher.commaMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 0));
+        assertEquals(1, matcher.isMatch(BUFFER1, 1));
+        assertEquals(0, matcher.isMatch(BUFFER1, 2));
     }
 
     @Test
     public void testDoubleQuoteMatcher() {
         final StrMatcher matcher = StrMatcher.doubleQuoteMatcher();
-        assertThat(StrMatcher.doubleQuoteMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 11)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 12)).isEqualTo(1);
+        assertSame(StrMatcher.doubleQuoteMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 11));
+        assertEquals(1, matcher.isMatch(BUFFER1, 12));
     }
 
     @Test
@@ -107,107 +107,107 @@ public class StrMatcherTest  {
         // all the onus is on the caller, so invalid inputs are not
         // the concern of StrMatcher, and are not bugs
         final StrMatcher matcher = StrMatcher.stringMatcher("bc");
-        assertThat(matcher.isMatch(BUFFER2, 1, 1, BUFFER2.length)).isEqualTo(2);
-        assertThat(matcher.isMatch(BUFFER2, 1, 0, 3)).isEqualTo(2);
-        assertThat(matcher.isMatch(BUFFER2, 1, 0, 2)).isEqualTo(0);
+        assertEquals(2, matcher.isMatch(BUFFER2, 1, 1, BUFFER2.length));
+        assertEquals(2, matcher.isMatch(BUFFER2, 1, 0, 3));
+        assertEquals(0, matcher.isMatch(BUFFER2, 1, 0, 2));
     }
 
     @Test
     public void testNoneMatcher() {
         final StrMatcher matcher = StrMatcher.noneMatcher();
-        assertThat(StrMatcher.noneMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 5)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 7)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 8)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 9)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 11)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 12)).isEqualTo(0);
+        assertSame(StrMatcher.noneMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 0));
+        assertEquals(0, matcher.isMatch(BUFFER1, 1));
+        assertEquals(0, matcher.isMatch(BUFFER1, 2));
+        assertEquals(0, matcher.isMatch(BUFFER1, 3));
+        assertEquals(0, matcher.isMatch(BUFFER1, 4));
+        assertEquals(0, matcher.isMatch(BUFFER1, 5));
+        assertEquals(0, matcher.isMatch(BUFFER1, 6));
+        assertEquals(0, matcher.isMatch(BUFFER1, 7));
+        assertEquals(0, matcher.isMatch(BUFFER1, 8));
+        assertEquals(0, matcher.isMatch(BUFFER1, 9));
+        assertEquals(0, matcher.isMatch(BUFFER1, 10));
+        assertEquals(0, matcher.isMatch(BUFFER1, 11));
+        assertEquals(0, matcher.isMatch(BUFFER1, 12));
     }
 
     @Test
     public void testQuoteMatcher() {
         final StrMatcher matcher = StrMatcher.quoteMatcher();
-        assertThat(StrMatcher.quoteMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 11)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 12)).isEqualTo(1);
+        assertSame(StrMatcher.quoteMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 10));
+        assertEquals(1, matcher.isMatch(BUFFER1, 11));
+        assertEquals(1, matcher.isMatch(BUFFER1, 12));
     }
 
     @Test
     public void testSingleQuoteMatcher() {
         final StrMatcher matcher = StrMatcher.singleQuoteMatcher();
-        assertThat(StrMatcher.singleQuoteMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 11)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 12)).isEqualTo(0);
+        assertSame(StrMatcher.singleQuoteMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 10));
+        assertEquals(1, matcher.isMatch(BUFFER1, 11));
+        assertEquals(0, matcher.isMatch(BUFFER1, 12));
     }
 
     @Test
     public void testSpaceMatcher() {
         final StrMatcher matcher = StrMatcher.spaceMatcher();
-        assertThat(StrMatcher.spaceMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 6)).isEqualTo(0);
+        assertSame(StrMatcher.spaceMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 4));
+        assertEquals(1, matcher.isMatch(BUFFER1, 5));
+        assertEquals(0, matcher.isMatch(BUFFER1, 6));
     }
 
     @Test
     public void testSplitMatcher() {
         final StrMatcher matcher = StrMatcher.splitMatcher();
-        assertThat(StrMatcher.splitMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 7)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 8)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 9)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 10)).isEqualTo(0);
+        assertSame(StrMatcher.splitMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 2));
+        assertEquals(1, matcher.isMatch(BUFFER1, 3));
+        assertEquals(0, matcher.isMatch(BUFFER1, 4));
+        assertEquals(1, matcher.isMatch(BUFFER1, 5));
+        assertEquals(0, matcher.isMatch(BUFFER1, 6));
+        assertEquals(1, matcher.isMatch(BUFFER1, 7));
+        assertEquals(1, matcher.isMatch(BUFFER1, 8));
+        assertEquals(1, matcher.isMatch(BUFFER1, 9));
+        assertEquals(0, matcher.isMatch(BUFFER1, 10));
     }
 
     @Test
     public void testStringMatcher_String() {
         final StrMatcher matcher = StrMatcher.stringMatcher("bc");
-        assertThat(matcher.isMatch(BUFFER2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 1)).isEqualTo(2);
-        assertThat(matcher.isMatch(BUFFER2, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER2, 5)).isEqualTo(0);
-        assertThat(StrMatcher.stringMatcher("")).isSameAs(StrMatcher.noneMatcher());
-        assertThat(StrMatcher.stringMatcher((String) null)).isSameAs(StrMatcher.noneMatcher());
+        assertEquals(0, matcher.isMatch(BUFFER2, 0));
+        assertEquals(2, matcher.isMatch(BUFFER2, 1));
+        assertEquals(0, matcher.isMatch(BUFFER2, 2));
+        assertEquals(0, matcher.isMatch(BUFFER2, 3));
+        assertEquals(0, matcher.isMatch(BUFFER2, 4));
+        assertEquals(0, matcher.isMatch(BUFFER2, 5));
+        assertSame(StrMatcher.stringMatcher(""), StrMatcher.noneMatcher());
+        assertSame(StrMatcher.stringMatcher((String) null), StrMatcher.noneMatcher());
     }
 
     @Test
     public void testTabMatcher() {
         final StrMatcher matcher = StrMatcher.tabMatcher();
-        assertThat(StrMatcher.tabMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 4)).isEqualTo(0);
+        assertSame(StrMatcher.tabMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 2));
+        assertEquals(1, matcher.isMatch(BUFFER1, 3));
+        assertEquals(0, matcher.isMatch(BUFFER1, 4));
     }
 
     @Test
     public void testTrimMatcher() {
         final StrMatcher matcher = StrMatcher.trimMatcher();
-        assertThat(StrMatcher.trimMatcher()).isSameAs(matcher);
-        assertThat(matcher.isMatch(BUFFER1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(BUFFER1, 7)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 8)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 9)).isEqualTo(1);
-        assertThat(matcher.isMatch(BUFFER1, 10)).isEqualTo(1);
+        assertSame(StrMatcher.trimMatcher(), matcher);
+        assertEquals(0, matcher.isMatch(BUFFER1, 2));
+        assertEquals(1, matcher.isMatch(BUFFER1, 3));
+        assertEquals(0, matcher.isMatch(BUFFER1, 4));
+        assertEquals(1, matcher.isMatch(BUFFER1, 5));
+        assertEquals(0, matcher.isMatch(BUFFER1, 6));
+        assertEquals(1, matcher.isMatch(BUFFER1, 7));
+        assertEquals(1, matcher.isMatch(BUFFER1, 8));
+        assertEquals(1, matcher.isMatch(BUFFER1, 9));
+        assertEquals(1, matcher.isMatch(BUFFER1, 10));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/StrSubstitutorTest.java b/src/test/java/org/apache/commons/text/StrSubstitutorTest.java
index c5768b33..051d8d3c 100644
--- a/src/test/java/org/apache/commons/text/StrSubstitutorTest.java
+++ b/src/test/java/org/apache/commons/text/StrSubstitutorTest.java
@@ -17,7 +17,6 @@
 
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThatNullPointerException;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNull;
@@ -657,7 +656,7 @@ public class StrSubstitutorTest {
 
     @Test
     public void testReplaceTakingThreeArgumentsThrowsNullPointerException() {
-        assertThatNullPointerException().isThrownBy(() -> StrSubstitutor.replace(null, (Properties) null));
+        assertThrows(NullPointerException.class, () -> StrSubstitutor.replace(null, (Properties) null));
     }
 
     /**
diff --git a/src/test/java/org/apache/commons/text/StringSubstitutorTest.java b/src/test/java/org/apache/commons/text/StringSubstitutorTest.java
index f4f51d05..97b18dde 100644
--- a/src/test/java/org/apache/commons/text/StringSubstitutorTest.java
+++ b/src/test/java/org/apache/commons/text/StringSubstitutorTest.java
@@ -17,13 +17,11 @@
 
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
-import static org.assertj.core.api.Assertions.assertThatNullPointerException;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.IOException;
@@ -60,21 +58,19 @@ public class StringSubstitutorTest {
     protected Map<String, String> values;
 
     private void assertEqualsCharSeq(final CharSequence expected, final CharSequence actual) {
-        assertEquals(expected, actual, () -> String.format("expected.length()=%,d, actual.length()=%,d",
-            StringUtils.length(expected), StringUtils.length(actual)));
+        assertEquals(expected, actual,
+                () -> String.format("expected.length()=%,d, actual.length()=%,d", StringUtils.length(expected), StringUtils.length(actual)));
     }
 
     protected void doNotReplace(final String replaceTemplate) throws IOException {
         doTestNoReplace(new StringSubstitutor(values), replaceTemplate);
     }
 
-    protected void doReplace(final String expectedResult, final String replaceTemplate, final boolean substring)
-        throws IOException {
+    protected void doReplace(final String expectedResult, final String replaceTemplate, final boolean substring) throws IOException {
         doTestReplace(new StringSubstitutor(values), expectedResult, replaceTemplate, substring);
     }
 
-    protected void doTestNoReplace(final StringSubstitutor substitutor, final String replaceTemplate)
-        throws IOException {
+    protected void doTestNoReplace(final StringSubstitutor substitutor, final String replaceTemplate) throws IOException {
         if (replaceTemplate == null) {
             assertNull(replace(substitutor, (String) null));
             assertNull(substitutor.replace((String) null, 0, 100));
@@ -97,15 +93,13 @@ public class StringSubstitutorTest {
         }
     }
 
-    protected void doTestReplace(final StringSubstitutor sub, final String expectedResult, final String replaceTemplate,
-        final boolean substring) throws IOException {
-        final String expectedShortResult = substring ? expectedResult.substring(1, expectedResult.length() - 1)
-            : expectedResult;
+    protected void doTestReplace(final StringSubstitutor sub, final String expectedResult, final String replaceTemplate, final boolean substring)
+            throws IOException {
+        final String expectedShortResult = substring ? expectedResult.substring(1, expectedResult.length() - 1) : expectedResult;
 
         // replace using String
         final String actual = replace(sub, replaceTemplate);
-        assertEquals(expectedResult, actual,
-            () -> String.format("Index of difference: %,d", StringUtils.indexOfDifference(expectedResult, actual)));
+        assertEquals(expectedResult, actual, () -> String.format("Index of difference: %,d", StringUtils.indexOfDifference(expectedResult, actual)));
         if (substring) {
             assertEquals(expectedShortResult, sub.replace(replaceTemplate, 1, replaceTemplate.length() - 2));
         }
@@ -228,12 +222,9 @@ public class StringSubstitutorTest {
         assertTrue(target.isEnableSubstitutionInVariables());
         assertTrue(target.isEnableUndefinedVariableException());
         assertEquals('e', target.getEscapeChar());
-        assertTrue(target.getValueDelimiterMatcher().toString().endsWith("['d']"),
-            target.getValueDelimiterMatcher().toString());
-        assertTrue(target.getVariablePrefixMatcher().toString().endsWith("['p']"),
-            target.getValueDelimiterMatcher().toString());
-        assertTrue(target.getVariableSuffixMatcher().toString().endsWith("['s']"),
-            target.getValueDelimiterMatcher().toString());
+        assertTrue(target.getValueDelimiterMatcher().toString().endsWith("['d']"), target.getValueDelimiterMatcher().toString());
+        assertTrue(target.getVariablePrefixMatcher().toString().endsWith("['p']"), target.getValueDelimiterMatcher().toString());
+        assertTrue(target.getVariableSuffixMatcher().toString().endsWith("['s']"), target.getValueDelimiterMatcher().toString());
     }
 
     /**
@@ -335,8 +326,7 @@ public class StringSubstitutorTest {
         doReplace("${11}", "$${${aa}}", false);
         doReplace("${111}", "$${${aaa}}", false);
         doReplace("${quick brown fox}", "$${${animal}}", false);
-        doReplace("The ${quick brown fox} jumps over the lazy dog.", "The $${${animal}} jumps over the ${target}.",
-            true);
+        doReplace("The ${quick brown fox} jumps over the lazy dog.", "The $${${animal}} jumps over the ${target}.", true);
         doReplace("${${a}}", "$${$${a}}", false);
         doReplace("${${aa}}", "$${$${aa}}", false);
         doReplace("${${aaa}}", "$${$${aaa}}", false);
@@ -346,7 +336,7 @@ public class StringSubstitutorTest {
         doReplace(".${${animal}}.", ".$${$${animal}}.", false);
         doReplace("The ${${animal}} jumps over the lazy dog.", "The $${$${animal}} jumps over the ${target}.", true);
         doReplace("The ${quick brown fox} jumps over the lazy dog. ${1234567890}.",
-            "The $${${animal}} jumps over the ${target}. $${${undefined.number:-1234567890}}.", true);
+                "The $${${animal}} jumps over the ${target}. $${${undefined.number:-1234567890}}.", true);
     }
 
     /**
@@ -451,24 +441,20 @@ public class StringSubstitutorTest {
         final StringSubstitutor sub = new StringSubstitutor(values);
         sub.setEnableUndefinedVariableException(true);
 
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> replace(sub, "The ${animal.${species}} jumps over the ${target}."))
-            .withMessage("Cannot resolve variable 'animal.${species' (enableSubstitutionInVariables=false).");
+        assertEquals("Cannot resolve variable 'animal.${species' (enableSubstitutionInVariables=false).",
+                assertThrows(IllegalArgumentException.class, () -> replace(sub, "The ${animal.${species}} jumps over the ${target}.")).getMessage());
 
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> replace(sub, "The ${animal.${species:-1}} jumps over the ${target}."))
-            .withMessage("Cannot resolve variable 'animal.${species:-1' (enableSubstitutionInVariables=false).");
+        assertEquals("Cannot resolve variable 'animal.${species:-1' (enableSubstitutionInVariables=false).",
+                assertThrows(IllegalArgumentException.class, () -> replace(sub, "The ${animal.${species:-1}} jumps over the ${target}.")).getMessage());
 
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> replace(sub, "The ${test:-statement} is a sample for missing ${unknown}."))
-            .withMessage("Cannot resolve variable 'unknown' (enableSubstitutionInVariables=false).");
+        assertEquals("Cannot resolve variable 'unknown' (enableSubstitutionInVariables=false).",
+                assertThrows(IllegalArgumentException.class, () -> replace(sub, "The ${test:-statement} is a sample for missing ${unknown}.")).getMessage());
 
         // if default value is available, exception will not be thrown
         assertEqualsCharSeq("The statement is a sample for missing variable.",
-            replace(sub, "The ${test:-statement} is a sample for missing ${unknown:-variable}."));
+                replace(sub, "The ${test:-statement} is a sample for missing ${unknown:-variable}."));
 
-        assertEqualsCharSeq("The fox jumps over the lazy dog.",
-            replace(sub, "The ${animal.1} jumps over the ${target}."));
+        assertEqualsCharSeq("The fox jumps over the lazy dog.", replace(sub, "The ${animal.1} jumps over the ${target}."));
     }
 
     /**
@@ -487,28 +473,25 @@ public class StringSubstitutorTest {
         sub.setEnableUndefinedVariableException(true);
         sub.setEnableSubstitutionInVariables(true);
 
-        assertEqualsCharSeq("The mouse jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species}} jumps over the ${target}."));
+        assertEqualsCharSeq("The mouse jumps over the lazy dog.", replace(sub, "The ${animal.${species}} jumps over the ${target}."));
         values.put("species", "1");
-        assertEqualsCharSeq("The fox jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species}} jumps over the ${target}."));
+        assertEqualsCharSeq("The fox jumps over the lazy dog.", replace(sub, "The ${animal.${species}} jumps over the ${target}."));
 
         // exception is thrown here because variable with name test.1 is missing
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> replace(sub, "The ${test.${statement}} is a sample for missing ${word}."))
-            .withMessage("Cannot resolve variable 'statement' (enableSubstitutionInVariables=true).");
+        assertEquals("Cannot resolve variable 'statement' (enableSubstitutionInVariables=true).",
+                assertThrows(IllegalArgumentException.class, () -> replace(sub, "The ${test.${statement}} is a sample for missing ${word}.")).getMessage());
 
         // exception is thrown here because variable with name test.2 is missing
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> replace(sub, "The ${test.${statement.${recursive}}} is a sample for missing ${word}."))
-            .withMessage("Cannot resolve variable 'test.2' (enableSubstitutionInVariables=true).");
+        assertEquals("Cannot resolve variable 'test.2' (enableSubstitutionInVariables=true).",
+                assertThrows(IllegalArgumentException.class, () -> replace(sub, "The ${test.${statement.${recursive}}} is a sample for missing ${word}."))
+                        .getMessage());
 
         assertEqualsCharSeq("statement", replace(sub, "${testok.${statement.${recursive}}}"));
 
         assertEqualsCharSeq("${testok.2}", replace(sub, "$${testok.${statement.${recursive}}}"));
 
         assertEqualsCharSeq("The statement is a sample for missing variable.",
-            replace(sub, "The ${testok.${statement.${recursive}}} is a sample for missing ${word}."));
+                replace(sub, "The ${testok.${statement.${recursive}}} is a sample for missing ${word}."));
     }
 
     /**
@@ -521,8 +504,7 @@ public class StringSubstitutorTest {
 
     @Test
     public void testReplaceInTakingStringBufferWithNonNull() {
-        final StringSubstitutor strSubstitutor = new StringSubstitutor(new HashMap<>(), "WV@i#y?N*[",
-            "WV@i#y?N*[", '*');
+        final StringSubstitutor strSubstitutor = new StringSubstitutor(new HashMap<>(), "WV@i#y?N*[", "WV@i#y?N*[", '*');
 
         assertFalse(strSubstitutor.isPreserveEscapes());
         assertFalse(strSubstitutor.replaceIn(new StringBuffer("WV@i#y?N*[")));
@@ -542,8 +524,7 @@ public class StringSubstitutorTest {
     @Test
     public void testReplaceInTakingStringBuilderWithNull() {
         final Map<String, Object> map = new HashMap<>();
-        final StringSubstitutor strSubstitutor = new StringSubstitutor(map, StringUtils.EMPTY, StringUtils.EMPTY, 'T',
-            "K+<'f");
+        final StringSubstitutor strSubstitutor = new StringSubstitutor(map, StringUtils.EMPTY, StringUtils.EMPTY, 'T', "K+<'f");
 
         assertFalse(strSubstitutor.replaceIn((StringBuilder) null));
     }
@@ -553,8 +534,7 @@ public class StringSubstitutorTest {
         final Map<String, Object> hashMap = new HashMap<>();
         final StringLookup mapStringLookup = StringLookupFactory.INSTANCE.mapStringLookup(hashMap);
         final StringMatcher strMatcher = StringMatcherFactory.INSTANCE.tabMatcher();
-        final StringSubstitutor strSubstitutor = new StringSubstitutor(mapStringLookup, strMatcher, strMatcher, 'b',
-            strMatcher);
+        final StringSubstitutor strSubstitutor = new StringSubstitutor(mapStringLookup, strMatcher, strMatcher, 'b', strMatcher);
 
         assertFalse(strSubstitutor.replaceIn((StringBuilder) null, 1315, -1369));
         assertEquals('b', strSubstitutor.getEscapeChar());
@@ -571,13 +551,11 @@ public class StringSubstitutorTest {
         values.put("species", "2");
         final StringSubstitutor sub = new StringSubstitutor(values);
         sub.setEnableSubstitutionInVariables(true);
-        assertEqualsCharSeq("The mouse jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species}} jumps over the ${target}."));
+        assertEqualsCharSeq("The mouse jumps over the lazy dog.", replace(sub, "The ${animal.${species}} jumps over the ${target}."));
         values.put("species", "1");
+        assertEqualsCharSeq("The fox jumps over the lazy dog.", replace(sub, "The ${animal.${species}} jumps over the ${target}."));
         assertEqualsCharSeq("The fox jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species}} jumps over the ${target}."));
-        assertEqualsCharSeq("The fox jumps over the lazy dog.", replace(sub,
-            "The ${unknown.animal.${unknown.species:-1}:-fox} " + "jumps over the ${unknow.target:-lazy dog}."));
+                replace(sub, "The ${unknown.animal.${unknown.species:-1}:-fox} " + "jumps over the ${unknow.target:-lazy dog}."));
     }
 
     /**
@@ -589,10 +567,8 @@ public class StringSubstitutorTest {
         values.put("animal.2", "mouse");
         values.put("species", "2");
         final StringSubstitutor sub = new StringSubstitutor(values);
-        assertEqualsCharSeq("The ${animal.${species}} jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species}} jumps over the ${target}."));
-        assertEqualsCharSeq("The ${animal.${species:-1}} jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species:-1}} jumps over the ${target}."));
+        assertEqualsCharSeq("The ${animal.${species}} jumps over the lazy dog.", replace(sub, "The ${animal.${species}} jumps over the ${target}."));
+        assertEqualsCharSeq("The ${animal.${species:-1}} jumps over the lazy dog.", replace(sub, "The ${animal.${species:-1}} jumps over the ${target}."));
     }
 
     /**
@@ -608,10 +584,9 @@ public class StringSubstitutorTest {
         final StringSubstitutor sub = new StringSubstitutor(values);
         sub.setEnableSubstitutionInVariables(true);
         assertEqualsCharSeq("white mouse", replace(sub, "${animal.${species.${color}}}"));
-        assertEqualsCharSeq("The white mouse jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species.${color}}} jumps over the ${target}."));
+        assertEqualsCharSeq("The white mouse jumps over the lazy dog.", replace(sub, "The ${animal.${species.${color}}} jumps over the ${target}."));
         assertEqualsCharSeq("The brown fox jumps over the lazy dog.",
-            replace(sub, "The ${animal.${species.${unknownColor:-brown}}} jumps over the ${target}."));
+                replace(sub, "The ${animal.${species.${unknownColor:-brown}}} jumps over the ${target}."));
     }
 
     /**
@@ -687,8 +662,7 @@ public class StringSubstitutorTest {
      */
     @Test
     public void testReplacePrefixNoSuffix() throws IOException {
-        doReplace("The ${animal jumps over the ${target} lazy dog.", "The ${animal jumps over the ${target} ${target}.",
-            true);
+        doReplace("The ${animal jumps over the ${target} lazy dog.", "The ${animal jumps over the ${target} ${target}.", true);
     }
 
     /**
@@ -753,7 +727,7 @@ public class StringSubstitutorTest {
 
     @Test
     public void testReplaceTakingThreeArgumentsThrowsNullPointerException() {
-        assertThatNullPointerException().isThrownBy(() -> StringSubstitutor.replace(null, (Properties) null));
+        assertThrows(NullPointerException.class, () -> StringSubstitutor.replace(null, (Properties) null));
     }
 
     @Test
@@ -763,19 +737,15 @@ public class StringSubstitutorTest {
         // replace(char[], int, int)
         final char[] emptyCharArray = {};
         // offset greater than array length
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(
-                () -> sub.replace(emptyCharArray, 0, 1));
+        assertThrows(StringIndexOutOfBoundsException.class, () -> sub.replace(emptyCharArray, 0, 1));
         // source != null && (offset > source.length || offset < 0)
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(
-                () -> sub.replace(emptyCharArray, 1, 0));
+        assertThrows(StringIndexOutOfBoundsException.class, () -> sub.replace(emptyCharArray, 1, 0));
 
         // replace(String, int, int)
         // offset greater than source length
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(
-                () -> sub.replace("", 1, 1));
+        assertThrows(StringIndexOutOfBoundsException.class, () -> sub.replace("", 1, 1));
         // source != null && offset >= 0 && offset <= source.length() && (length > -offset + source.length() || length < 0)
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(
-                () -> sub.replace("", 0, 1));
+        assertThrows(StringIndexOutOfBoundsException.class, () -> sub.replace("", 0, 1));
     }
 
     /**
@@ -801,8 +771,7 @@ public class StringSubstitutorTest {
      */
     @Test
     public void testReplaceUnknownKeyDefaultValue() throws IOException {
-        doReplace("The ${person} jumps over the lazy dog. 1234567890.",
-            "The ${person} jumps over the ${target}. ${undefined.number:-1234567890}.", true);
+        doReplace("The ${person} jumps over the lazy dog. 1234567890.", "The ${person} jumps over the ${target}. ${undefined.number:-1234567890}.", true);
     }
 
     /**
@@ -1007,8 +976,7 @@ public class StringSubstitutorTest {
         map.put("name", "commons");
         final StringSubstitutor sub = new StringSubstitutor(map) {
             @Override
-            protected String resolveVariable(final String variableName, final TextStringBuilder buf, final int startPos,
-                final int endPos) {
+            protected String resolveVariable(final String variableName, final TextStringBuilder buf, final int startPos, final int endPos) {
                 assertEquals("name", variableName);
                 assertSame(builder, buf);
                 assertEquals(3, startPos);
@@ -1027,8 +995,7 @@ public class StringSubstitutorTest {
         map.put(" there ", "XXX");
         map.put("name", "commons");
         assertEqualsCharSeq("Hi commons!", StringSubstitutor.replace("Hi @name@!", map, "@", "@"));
-        assertEqualsCharSeq("Hello there commons!",
-            StringSubstitutor.replace("@greeting@ there @name@!", map, "@", "@"));
+        assertEqualsCharSeq("Hello there commons!", StringSubstitutor.replace("@greeting@ there @name@!", map, "@", "@"));
     }
 
     /**
@@ -1062,8 +1029,8 @@ public class StringSubstitutorTest {
         buf.append(SystemProperties.getOsName());
         buf.append(", your home directory is ");
         buf.append(SystemProperties.getUserHome()).append('.');
-        assertEqualsCharSeq(buf.toString(), StringSubstitutor.replaceSystemProperties(
-            "Hi ${user.name}, you are " + "working with ${os.name}, your home " + "directory is ${user.home}."));
+        assertEqualsCharSeq(buf.toString(),
+                StringSubstitutor.replaceSystemProperties("Hi ${user.name}, you are " + "working with ${os.name}, your home " + "directory is ${user.home}."));
     }
 
     /**
diff --git a/src/test/java/org/apache/commons/text/TextStringBuilderAppendInsertTest.java b/src/test/java/org/apache/commons/text/TextStringBuilderAppendInsertTest.java
index 3ea31f7a..ad021dd8 100644
--- a/src/test/java/org/apache/commons/text/TextStringBuilderAppendInsertTest.java
+++ b/src/test/java/org/apache/commons/text/TextStringBuilderAppendInsertTest.java
@@ -17,7 +17,7 @@
 
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
@@ -55,38 +55,38 @@ public class TextStringBuilderAppendInsertTest {
     public void testAppend_Boolean() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append(true);
-        assertThat(sb.toString()).isEqualTo("true");
+        assertEquals("true", sb.toString());
 
         sb.append(false);
-        assertThat(sb.toString()).isEqualTo("truefalse");
+        assertEquals("truefalse", sb.toString());
 
         sb.append('!');
-        assertThat(sb.toString()).isEqualTo("truefalse!");
+        assertEquals("truefalse!", sb.toString());
     }
 
     @Test
     public void testAppend_CharArray() {
         TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("NULL").append((char[]) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append(ArrayUtils.EMPTY_CHAR_ARRAY);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.append(new char[] {'f', 'o', 'o'});
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
     }
 
     @Test
     public void testAppend_CharArray_int_int() {
         final TextStringBuilder sb0 = new TextStringBuilder();
         sb0.setNullText("NULL").append((char[]) null, 0, 1);
-        assertThat(sb0.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb0.toString());
 
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append(new char[] {'f', 'o', 'o'}, 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append(new char[] {'b', 'a', 'r'}, -1, 1),
             "append(char[], -1,) expected IndexOutOfBoundsException");
@@ -107,10 +107,10 @@ public class TextStringBuilderAppendInsertTest {
             "append(char[], 4, 0) expected IndexOutOfBoundsException");
 
         sb.append(new char[] {'b', 'a', 'r'}, 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new char[] {'a', 'b', 'c', 'b', 'a', 'r', 'd', 'e', 'f'}, 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
@@ -119,94 +119,94 @@ public class TextStringBuilderAppendInsertTest {
 
         sb = new TextStringBuilder();
         sb.append("Hi", (Object[]) null);
-        assertThat(sb.toString()).isEqualTo("Hi");
+        assertEquals("Hi", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append("Hi", "Alice");
-        assertThat(sb.toString()).isEqualTo("Hi");
+        assertEquals("Hi", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append("Hi %s", "Alice");
-        assertThat(sb.toString()).isEqualTo("Hi Alice");
+        assertEquals("Hi Alice", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append("Hi %s %,d", "Alice", 5000);
         // group separator depends on system locale
         final char groupingSeparator = DecimalFormatSymbols.getInstance().getGroupingSeparator();
         final String expected = "Hi Alice 5" + groupingSeparator + "000";
-        assertThat(sb.toString()).isEqualTo(expected);
+        assertEquals(expected, sb.toString());
     }
 
     @Test
     public void testAppend_Object() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendNull();
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.append((Object) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.append(FOO);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append((StringBuffer) null);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer("baz"));
-        assertThat(sb.toString()).isEqualTo("foobaz");
+        assertEquals("foobaz", sb.toString());
 
         sb.append(new TextStringBuilder("yes"));
-        assertThat(sb.toString()).isEqualTo("foobazyes");
+        assertEquals("foobazyes", sb.toString());
 
         sb.append((CharSequence) "Seq");
-        assertThat(sb.toString()).isEqualTo("foobazyesSeq");
+        assertEquals("foobazyesSeq", sb.toString());
 
         sb.append(new StringBuilder("bld")); // Check it supports StringBuilder
-        assertThat(sb.toString()).isEqualTo("foobazyesSeqbld");
+        assertEquals("foobazyesSeqbld", sb.toString());
     }
 
     @Test
     public void testAppend_PrimitiveNumber() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append(0);
-        assertThat(sb.toString()).isEqualTo("0");
+        assertEquals("0", sb.toString());
 
         sb.append(1L);
-        assertThat(sb.toString()).isEqualTo("01");
+        assertEquals("01", sb.toString());
 
         sb.append(2.3f);
-        assertThat(sb.toString()).isEqualTo("012.3");
+        assertEquals("012.3", sb.toString());
 
         sb.append(4.5d);
-        assertThat(sb.toString()).isEqualTo("012.34.5");
+        assertEquals("012.34.5", sb.toString());
     }
 
     @Test
     public void testAppend_String() {
         TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("NULL").append((String) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append("");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append("bar");
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_String_int_int() {
         final TextStringBuilder sb0 = new TextStringBuilder();
         sb0.setNullText("NULL").append((String) null, 0, 1);
-        assertThat(sb0.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb0.toString());
 
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append("foo", 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append("bar", -1, 1), "append(char[], -1,) expected IndexOutOfBoundsException");
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append("bar", 3, 1), "append(char[], 3,) expected IndexOutOfBoundsException");
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append("bar", 1, -1), "append(char[],, -1) expected IndexOutOfBoundsException");
@@ -219,41 +219,41 @@ public class TextStringBuilderAppendInsertTest {
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append((CharSequence) "bar", 2, 0), "append(char[], 2, 0) expected IndexOutOfBoundsException");
 
         sb.append("bar", 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append("abcbardef", 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
 
         sb.append((CharSequence) "abcbardef", 4, 7);
-        assertThat(sb.toString()).isEqualTo("foobarard");
+        assertEquals("foobarard", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuffer() {
         TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("NULL").append((StringBuffer) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append(new StringBuffer("foo"));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer(""));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer("bar"));
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuffer_int_int() {
         final TextStringBuilder sb0 = new TextStringBuilder();
         sb0.setNullText("NULL").append((StringBuffer) null, 0, 1);
-        assertThat(sb0.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb0.toString());
 
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append(new StringBuffer("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append(new StringBuffer("bar"), -1, 1),
             "append(char[], -1,) expected IndexOutOfBoundsException");
@@ -273,38 +273,38 @@ public class TextStringBuilderAppendInsertTest {
             "append(char[], 4, 0) expected IndexOutOfBoundsException");
 
         sb.append(new StringBuffer("bar"), 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuffer("abcbardef"), 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuilder() {
         TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("NULL").append((String) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append(new StringBuilder("foo"));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuilder(""));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuilder("bar"));
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_StringBuilder_int_int() {
         final TextStringBuilder sb0 = new TextStringBuilder();
         sb0.setNullText("NULL").append((String) null, 0, 1);
-        assertThat(sb0.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb0.toString());
 
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append(new StringBuilder("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append(new StringBuilder("bar"), -1, 1),
             "append(StringBuilder, -1,) expected IndexOutOfBoundsException");
@@ -325,41 +325,41 @@ public class TextStringBuilderAppendInsertTest {
             "append(StringBuilder, 4, 0) expected IndexOutOfBoundsException");
 
         sb.append(new StringBuilder("bar"), 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new StringBuilder("abcbardef"), 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
 
         sb.append(new StringBuilder("abcbardef"), 4, 3);
-        assertThat(sb.toString()).isEqualTo("foobarard");
+        assertEquals("foobarard", sb.toString());
     }
 
     @Test
     public void testAppend_TextStringBuilder() {
         TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("NULL").append((TextStringBuilder) null);
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb = new TextStringBuilder();
         sb.append(new TextStringBuilder("foo"));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new TextStringBuilder(""));
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new TextStringBuilder("bar"));
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppend_TextStringBuilder_int_int() {
         final TextStringBuilder sb0 = new TextStringBuilder();
         sb0.setNullText("NULL").append((TextStringBuilder) null, 0, 1);
-        assertThat(sb0.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb0.toString());
 
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append(new TextStringBuilder("foo"), 0, 3);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.append(new TextStringBuilder("bar"), -1, 1),
             "append(char[], -1,) expected IndexOutOfBoundsException");
@@ -380,212 +380,212 @@ public class TextStringBuilderAppendInsertTest {
             "append(char[], 4, 0) expected IndexOutOfBoundsException");
 
         sb.append(new TextStringBuilder("bar"), 3, 0);
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.append(new TextStringBuilder("abcbardef"), 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobar");
+        assertEquals("foobar", sb.toString());
     }
 
     @Test
     public void testAppendAll_Array() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendAll((Object[]) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll();
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll("foo", "bar", "baz");
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.appendAll("foo", "bar", "baz");
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
     }
 
     @Test
     public void testAppendAll_Collection() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendAll((Collection<?>) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Collections.EMPTY_LIST);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Arrays.asList("foo", "bar", "baz"));
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
     }
 
     @Test
     public void testAppendAll_Iterator() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendAll((Iterator<?>) null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Collections.EMPTY_LIST.iterator());
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendAll(Arrays.asList("foo", "bar", "baz").iterator());
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadLeft() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendFixedWidthPadLeft("foo", -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 1, '-');
-        assertThat(sb.toString()).isEqualTo("o");
+        assertEquals("o", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 2, '-');
-        assertThat(sb.toString()).isEqualTo("oo");
+        assertEquals("oo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 3, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 4, '-');
-        assertThat(sb.toString()).isEqualTo("-foo");
+        assertEquals("-foo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft("foo", 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
+        assertEquals(10, sb.length());
         // 1234567890
-        assertThat(sb.toString()).isEqualTo("-------foo");
+        assertEquals("-------foo", sb.toString());
 
         sb.clear();
         sb.setNullText("null");
         sb.appendFixedWidthPadLeft(null, 5, '-');
-        assertThat(sb.toString()).isEqualTo("-null");
+        assertEquals("-null", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadLeft_int() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendFixedWidthPadLeft(123, -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 1, '-');
-        assertThat(sb.toString()).isEqualTo("3");
+        assertEquals("3", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 2, '-');
-        assertThat(sb.toString()).isEqualTo("23");
+        assertEquals("23", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 3, '-');
-        assertThat(sb.toString()).isEqualTo("123");
+        assertEquals("123", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 4, '-');
-        assertThat(sb.toString()).isEqualTo("-123");
+        assertEquals("-123", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadLeft(123, 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
+        assertEquals(10, sb.length());
         // 1234567890
-        assertThat(sb.toString()).isEqualTo("-------123");
+        assertEquals("-------123", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadRight() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendFixedWidthPadRight("foo", -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 1, '-');
-        assertThat(sb.toString()).isEqualTo("f");
+        assertEquals("f", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 2, '-');
-        assertThat(sb.toString()).isEqualTo("fo");
+        assertEquals("fo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 3, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 4, '-');
-        assertThat(sb.toString()).isEqualTo("foo-");
+        assertEquals("foo-", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight("foo", 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
+        assertEquals(10, sb.length());
         // 1234567890
-        assertThat(sb.toString()).isEqualTo("foo-------");
+        assertEquals("foo-------", sb.toString());
 
         sb.clear();
         sb.setNullText("null");
         sb.appendFixedWidthPadRight(null, 5, '-');
-        assertThat(sb.toString()).isEqualTo("null-");
+        assertEquals("null-", sb.toString());
     }
 
     @Test
     public void testAppendFixedWidthPadRight_int() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendFixedWidthPadRight(123, -1, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 0, '-');
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 1, '-');
-        assertThat(sb.toString()).isEqualTo("1");
+        assertEquals("1", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 2, '-');
-        assertThat(sb.toString()).isEqualTo("12");
+        assertEquals("12", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 3, '-');
-        assertThat(sb.toString()).isEqualTo("123");
+        assertEquals("123", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 4, '-');
-        assertThat(sb.toString()).isEqualTo("123-");
+        assertEquals("123-", sb.toString());
 
         sb.clear();
         sb.appendFixedWidthPadRight(123, 10, '-');
-        assertThat(sb.length()).isEqualTo(10);
+        assertEquals(10, sb.length());
         // 1234567890
-        assertThat(sb.toString()).isEqualTo("123-------");
+        assertEquals("123-------", sb.toString());
     }
 
     @Test
     public void testAppendln_Boolean() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendln(true);
-        assertThat(sb.toString()).isEqualTo("true" + SEP);
+        assertEquals("true" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(false);
-        assertThat(sb.toString()).isEqualTo("false" + SEP);
+        assertEquals("false" + SEP, sb.toString());
     }
 
     @Test
@@ -594,7 +594,7 @@ public class TextStringBuilderAppendInsertTest {
         final char[] input = "foo".toCharArray();
         sb.appendln(input);
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(input);
         verify(sb, times(1)).appendNewLine();
@@ -606,7 +606,7 @@ public class TextStringBuilderAppendInsertTest {
         final char[] input = "foo".toCharArray();
         sb.appendln(input, 0, 3);
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(input, 0, 3);
         verify(sb, times(1)).appendNewLine();
@@ -617,7 +617,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln("Hello %s", "Alice");
 
-        assertThat(sb.toString()).isEqualTo("Hello Alice" + SEP);
+        assertEquals("Hello Alice" + SEP, sb.toString());
 
         verify(sb, times(2)).append(anyString()); // appendNewLine() calls append(String)
         verify(sb, times(1)).appendNewLine();
@@ -627,32 +627,32 @@ public class TextStringBuilderAppendInsertTest {
     public void testAppendln_Object() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendln((Object) null);
-        assertThat(sb.toString()).isEqualTo("" + SEP);
+        assertEquals("" + SEP, sb.toString());
 
         sb.appendln(FOO);
-        assertThat(sb.toString()).isEqualTo(SEP + "foo" + SEP);
+        assertEquals(SEP + "foo" + SEP, sb.toString());
 
         sb.appendln(Integer.valueOf(6));
-        assertThat(sb.toString()).isEqualTo(SEP + "foo" + SEP + "6" + SEP);
+        assertEquals(SEP + "foo" + SEP + "6" + SEP, sb.toString());
     }
 
     @Test
     public void testAppendln_PrimitiveNumber() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendln(0);
-        assertThat(sb.toString()).isEqualTo("0" + SEP);
+        assertEquals("0" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(1L);
-        assertThat(sb.toString()).isEqualTo("1" + SEP);
+        assertEquals("1" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(2.3f);
-        assertThat(sb.toString()).isEqualTo("2.3" + SEP);
+        assertEquals("2.3" + SEP, sb.toString());
 
         sb.clear();
         sb.appendln(4.5d);
-        assertThat(sb.toString()).isEqualTo("4.5" + SEP);
+        assertEquals("4.5" + SEP, sb.toString());
     }
 
     @Test
@@ -660,7 +660,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln("foo");
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(2)).append(anyString()); // appendNewLine() calls append(String)
         verify(sb, times(1)).appendNewLine();
@@ -671,7 +671,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln("foo", 0, 3);
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(2)).append(anyString(), anyInt(), anyInt()); // appendNewLine() calls append(String)
         verify(sb, times(1)).appendNewLine();
@@ -682,7 +682,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln(new StringBuffer("foo"));
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(any(StringBuffer.class));
         verify(sb, times(1)).appendNewLine();
@@ -693,7 +693,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln(new StringBuffer("foo"), 0, 3);
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(any(StringBuffer.class), anyInt(), anyInt());
         verify(sb, times(1)).appendNewLine();
@@ -704,7 +704,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln(new StringBuilder("foo"));
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(any(StringBuilder.class));
         verify(sb, times(1)).appendNewLine();
@@ -715,7 +715,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln(new StringBuilder("foo"), 0, 3);
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(any(StringBuilder.class), anyInt(), anyInt());
         verify(sb, times(1)).appendNewLine();
@@ -726,7 +726,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln(new TextStringBuilder("foo"));
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(any(TextStringBuilder.class));
         verify(sb, times(1)).appendNewLine();
@@ -737,7 +737,7 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = spy(new TextStringBuilder());
         sb.appendln(new TextStringBuilder("foo"), 0, 3);
 
-        assertThat(sb.toString()).isEqualTo("foo" + SEP);
+        assertEquals("foo" + SEP, sb.toString());
 
         verify(sb, times(1)).append(any(TextStringBuilder.class), anyInt(), anyInt());
         verify(sb, times(1)).appendNewLine();
@@ -747,43 +747,43 @@ public class TextStringBuilderAppendInsertTest {
     public void testAppendNewLine() {
         TextStringBuilder sb = new TextStringBuilder("---");
         sb.appendNewLine().append("+++");
-        assertThat(sb.toString()).isEqualTo("---" + SEP + "+++");
+        assertEquals("---" + SEP + "+++", sb.toString());
 
         sb = new TextStringBuilder("---");
         sb.setNewLineText("#").appendNewLine().setNewLineText(null).appendNewLine();
-        assertThat(sb.toString()).isEqualTo("---#" + SEP);
+        assertEquals("---#" + SEP, sb.toString());
     }
 
     @Test
     public void testAppendPadding() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.appendPadding(-1, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.appendPadding(0, '-');
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
 
         sb.appendPadding(1, '-');
-        assertThat(sb.toString()).isEqualTo("foo-");
+        assertEquals("foo-", sb.toString());
 
         sb.appendPadding(16, '-');
-        assertThat(sb.length()).isEqualTo(20);
+        assertEquals(20, sb.length());
         // 12345678901234567890
-        assertThat(sb.toString()).isEqualTo("foo-----------------");
+        assertEquals("foo-----------------", sb.toString());
     }
 
     @Test
     public void testAppendSeparator_char() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendSeparator(','); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(',');
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
@@ -793,58 +793,58 @@ public class TextStringBuilderAppendInsertTest {
         final char standardSeparator = ',';
         final String foo = "foo";
         sb.appendSeparator(standardSeparator, startSeparator); // no effect
-        assertThat(sb.toString()).isEqualTo(String.valueOf(startSeparator));
+        assertEquals(String.valueOf(startSeparator), sb.toString());
         sb.append(foo);
-        assertThat(sb.toString()).isEqualTo(String.valueOf(startSeparator) + foo);
+        assertEquals(String.valueOf(startSeparator) + foo, sb.toString());
         sb.appendSeparator(standardSeparator, startSeparator);
-        assertThat(sb.toString()).isEqualTo(String.valueOf(startSeparator) + foo + standardSeparator);
+        assertEquals(String.valueOf(startSeparator) + foo + standardSeparator, sb.toString());
     }
 
     @Test
     public void testAppendSeparator_char_int() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendSeparator(',', 0); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(',', 1);
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
 
         sb.appendSeparator(',', -1); // no effect
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
     public void testAppendSeparator_String() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendSeparator(","); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(",");
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
     public void testAppendSeparator_String_int() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendSeparator(null, -1); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(null, 0); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(null, 1); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(",", -1); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(",", 0); // no effect
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.append("foo");
-        assertThat(sb.toString()).isEqualTo("foo");
+        assertEquals("foo", sb.toString());
         sb.appendSeparator(",", 1);
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
 
         sb.appendSeparator(",", -1); // no effect
-        assertThat(sb.toString()).isEqualTo("foo,");
+        assertEquals("foo,", sb.toString());
     }
 
     @Test
@@ -854,119 +854,119 @@ public class TextStringBuilderAppendInsertTest {
         final String standardSeparator = ",";
         final String foo = "foo";
         sb.appendSeparator(null, null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(standardSeparator, null);
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
         sb.appendSeparator(standardSeparator, startSeparator);
-        assertThat(sb.toString()).isEqualTo(startSeparator);
+        assertEquals(startSeparator, sb.toString());
         sb.appendSeparator(null, null);
-        assertThat(sb.toString()).isEqualTo(startSeparator);
+        assertEquals(startSeparator, sb.toString());
         sb.appendSeparator(null, startSeparator);
-        assertThat(sb.toString()).isEqualTo(startSeparator);
+        assertEquals(startSeparator, sb.toString());
         sb.append(foo);
-        assertThat(sb.toString()).isEqualTo(startSeparator + foo);
+        assertEquals(startSeparator + foo, sb.toString());
         sb.appendSeparator(standardSeparator, startSeparator);
-        assertThat(sb.toString()).isEqualTo(startSeparator + foo + standardSeparator);
+        assertEquals(startSeparator + foo + standardSeparator, sb.toString());
     }
 
     @Test
     public void testAppendWithNullText() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("NULL");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.appendNull();
-        assertThat(sb.toString()).isEqualTo("NULL");
+        assertEquals("NULL", sb.toString());
 
         sb.append((Object) null);
-        assertThat(sb.toString()).isEqualTo("NULLNULL");
+        assertEquals("NULLNULL", sb.toString());
 
         sb.append(FOO);
-        assertThat(sb.toString()).isEqualTo("NULLNULLfoo");
+        assertEquals("NULLNULLfoo", sb.toString());
 
         sb.append((String) null);
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULL");
+        assertEquals("NULLNULLfooNULL", sb.toString());
 
         sb.append("");
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULL");
+        assertEquals("NULLNULLfooNULL", sb.toString());
 
         sb.append("bar");
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULLbar");
+        assertEquals("NULLNULLfooNULLbar", sb.toString());
 
         sb.append((StringBuffer) null);
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULLbarNULL");
+        assertEquals("NULLNULLfooNULLbarNULL", sb.toString());
 
         sb.append(new StringBuffer("baz"));
-        assertThat(sb.toString()).isEqualTo("NULLNULLfooNULLbarNULLbaz");
+        assertEquals("NULLNULLfooNULLbarNULLbaz", sb.toString());
     }
 
     @Test
     public void testAppendWithSeparators_Array() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendWithSeparators((Object[]) null, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(ArrayUtils.EMPTY_OBJECT_ARRAY, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(new Object[] {"foo", "bar", "baz"}, ",");
-        assertThat(sb.toString()).isEqualTo("foo,bar,baz");
+        assertEquals("foo,bar,baz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(new Object[] {"foo", "bar", "baz"}, null);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(new Object[] {"foo", null, "baz"}, ",");
-        assertThat(sb.toString()).isEqualTo("foo,,baz");
+        assertEquals("foo,,baz", sb.toString());
     }
 
     @Test
     public void testAppendWithSeparators_Collection() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendWithSeparators((Collection<?>) null, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Collections.EMPTY_LIST, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz"), ",");
-        assertThat(sb.toString()).isEqualTo("foo,bar,baz");
+        assertEquals("foo,bar,baz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz"), null);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", null, "baz"), ",");
-        assertThat(sb.toString()).isEqualTo("foo,,baz");
+        assertEquals("foo,,baz", sb.toString());
     }
 
     @Test
     public void testAppendWithSeparators_Iterator() {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.appendWithSeparators((Iterator<?>) null, ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Collections.EMPTY_LIST.iterator(), ",");
-        assertThat(sb.toString()).isEqualTo("");
+        assertEquals("", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz").iterator(), ",");
-        assertThat(sb.toString()).isEqualTo("foo,bar,baz");
+        assertEquals("foo,bar,baz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", "bar", "baz").iterator(), null);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", null, "baz").iterator(), ",");
-        assertThat(sb.toString()).isEqualTo("foo,,baz");
+        assertEquals("foo,,baz", sb.toString());
     }
 
     @Test
@@ -974,11 +974,11 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("null");
         sb.appendWithSeparators(new Object[] {"foo", null, "baz"}, ",");
-        assertThat(sb.toString()).isEqualTo("foo,null,baz");
+        assertEquals("foo,null,baz", sb.toString());
 
         sb.clear();
         sb.appendWithSeparators(Arrays.asList("foo", null, "baz"), ",");
-        assertThat(sb.toString()).isEqualTo("foo,null,baz");
+        assertEquals("foo,null,baz", sb.toString());
     }
 
     @Test
@@ -986,52 +986,52 @@ public class TextStringBuilderAppendInsertTest {
 
         final TextStringBuilder sb = new TextStringBuilder();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, FOO));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, FOO));
 
         sb.insert(0, (Object) null);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, FOO);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, "foo"));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, "foo"));
 
         sb.insert(0, (String) null);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, "foo");
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, new char[] {'f', 'o', 'o'}));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, new char[] {'f', 'o', 'o'}));
 
         sb.insert(0, (char[]) null);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, ArrayUtils.EMPTY_CHAR_ARRAY);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, new char[] {'f', 'o', 'o'});
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class,
             () -> sb.insert(-1, new char[] {'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 3, 3));
@@ -1040,10 +1040,10 @@ public class TextStringBuilderAppendInsertTest {
             () -> sb.insert(7, new char[] {'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 3, 3));
 
         sb.insert(0, (char[]) null, 0, 0);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, ArrayUtils.EMPTY_CHAR_ARRAY, 0, 0);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class,
             () -> sb.insert(0, new char[] {'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, -1, 3));
@@ -1058,79 +1058,79 @@ public class TextStringBuilderAppendInsertTest {
             () -> sb.insert(0, new char[] {'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 0, 10));
 
         sb.insert(0, new char[] {'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 0, 0);
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         sb.insert(0, new char[] {'a', 'b', 'c', 'f', 'o', 'o', 'd', 'e', 'f'}, 3, 3);
-        assertThat(sb.toString()).isEqualTo("foobarbaz");
+        assertEquals("foobarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, true));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, true));
 
         sb.insert(0, true);
-        assertThat(sb.toString()).isEqualTo("truebarbaz");
+        assertEquals("truebarbaz", sb.toString());
 
         sb.insert(0, false);
-        assertThat(sb.toString()).isEqualTo("falsetruebarbaz");
+        assertEquals("falsetruebarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, '!'));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, '!'));
 
         sb.insert(0, '!');
-        assertThat(sb.toString()).isEqualTo("!barbaz");
+        assertEquals("!barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 0));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 0));
 
         sb.insert(0, '0');
-        assertThat(sb.toString()).isEqualTo("0barbaz");
+        assertEquals("0barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 1L));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 1L));
 
         sb.insert(0, 1L);
-        assertThat(sb.toString()).isEqualTo("1barbaz");
+        assertEquals("1barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 2.3F));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 2.3F));
 
         sb.insert(0, 2.3F);
-        assertThat(sb.toString()).isEqualTo("2.3barbaz");
+        assertEquals("2.3barbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, 4.5D));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, 4.5D));
 
         sb.insert(0, 4.5D);
-        assertThat(sb.toString()).isEqualTo("4.5barbaz");
+        assertEquals("4.5barbaz", sb.toString());
     }
 
     @Test
@@ -1138,37 +1138,37 @@ public class TextStringBuilderAppendInsertTest {
         final TextStringBuilder sb = new TextStringBuilder();
         sb.setNullText("null");
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, FOO));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, FOO));
 
         sb.insert(0, (Object) null);
-        assertThat(sb.toString()).isEqualTo("nullbarbaz");
+        assertEquals("nullbarbaz", sb.toString());
 
         sb.insert(0, FOO);
-        assertThat(sb.toString()).isEqualTo("foonullbarbaz");
+        assertEquals("foonullbarbaz", sb.toString());
 
         sb.clear();
         sb.append("barbaz");
-        assertThat(sb.toString()).isEqualTo("barbaz");
+        assertEquals("barbaz", sb.toString());
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(-1, "foo"));
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.insert(7, "foo"));
 
         sb.insert(0, (String) null);
-        assertThat(sb.toString()).isEqualTo("nullbarbaz");
+        assertEquals("nullbarbaz", sb.toString());
 
         sb.insert(0, "foo");
-        assertThat(sb.toString()).isEqualTo("foonullbarbaz");
+        assertEquals("foonullbarbaz", sb.toString());
 
         sb.insert(0, (char[]) null);
-        assertThat(sb.toString()).isEqualTo("nullfoonullbarbaz");
+        assertEquals("nullfoonullbarbaz", sb.toString());
 
         sb.insert(0, (char[]) null, 0, 0);
-        assertThat(sb.toString()).isEqualTo("nullnullfoonullbarbaz");
+        assertEquals("nullnullfoonullbarbaz", sb.toString());
     }
 
     /** See: https://issues.apache.org/jira/browse/LANG-299 */
@@ -1176,6 +1176,6 @@ public class TextStringBuilderAppendInsertTest {
     public void testLang299() {
         final TextStringBuilder sb = new TextStringBuilder(1);
         sb.appendFixedWidthPadRight("foo", 1, '-');
-        assertThat(sb.toString()).isEqualTo("f");
+        assertEquals("f", sb.toString());
     }
 }
diff --git a/src/test/java/org/apache/commons/text/TextStringBuilderTest.java b/src/test/java/org/apache/commons/text/TextStringBuilderTest.java
index 524ae3c5..16d0c21c 100644
--- a/src/test/java/org/apache/commons/text/TextStringBuilderTest.java
+++ b/src/test/java/org/apache/commons/text/TextStringBuilderTest.java
@@ -17,7 +17,6 @@
 
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -80,7 +79,7 @@ public class TextStringBuilderTest {
     /**
      * Clear the string builder and fill up to the specified length.
      *
-     * @param sb the string builder
+     * @param sb     the string builder
      * @param length the length
      */
     private static void fill(final TextStringBuilder sb, final int length) {
@@ -202,7 +201,7 @@ public class TextStringBuilderTest {
 
     @Test
     public void testAppendTakingTwoIntsWithIndexOutOfBoundsThrowsStringIndexOutOfBoundsExceptionTwo() {
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(() -> {
+        assertThrows(StringIndexOutOfBoundsException.class, () -> {
             final Charset charset = Charset.defaultCharset();
             final ByteBuffer byteBuffer = charset.encode("asdf");
             final CharBuffer charBuffer = charset.decode(byteBuffer);
@@ -213,7 +212,7 @@ public class TextStringBuilderTest {
 
     @Test
     public void testAppendTakingTwoIntsWithZeroThrowsStringIndexOutOfBoundsException() {
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(() -> {
+        assertThrows(StringIndexOutOfBoundsException.class, () -> {
             final Charset charset = Charset.defaultCharset();
             final ByteBuffer byteBuffer = charset.encode("end < start");
             final CharBuffer charBuffer = charset.decode(byteBuffer);
@@ -323,8 +322,7 @@ public class TextStringBuilderTest {
             assertThrows(IndexOutOfBoundsException.class, () -> reader.read(array, 0, -1));
             assertThrows(IndexOutOfBoundsException.class, () -> reader.read(array, 100, 1));
             assertThrows(IndexOutOfBoundsException.class, () -> reader.read(array, 0, 100));
-            assertThrows(IndexOutOfBoundsException.class,
-                () -> reader.read(array, Integer.MAX_VALUE, Integer.MAX_VALUE));
+            assertThrows(IndexOutOfBoundsException.class, () -> reader.read(array, Integer.MAX_VALUE, Integer.MAX_VALUE));
 
             assertEquals(0, reader.read(array, 0, 0));
             assertEquals(0, array[0]);
@@ -392,10 +390,10 @@ public class TextStringBuilderTest {
             writer.write('l');
             assertEquals("basel", sb.toString());
 
-            writer.write(new char[] {'i', 'n'});
+            writer.write(new char[] { 'i', 'n' });
             assertEquals("baselin", sb.toString());
 
-            writer.write(new char[] {'n', 'e', 'r'}, 1, 2);
+            writer.write(new char[] { 'n', 'e', 'r' }, 1, 2);
             assertEquals("baseliner", sb.toString());
 
             writer.write(" rout");
@@ -724,7 +722,7 @@ public class TextStringBuilderTest {
 
     @Test
     public void testDeleteCharAtWithNegative() {
-        assertThatExceptionOfType(StringIndexOutOfBoundsException.class).isThrownBy(() -> new TextStringBuilder().deleteCharAt(-1258));
+        assertThrows(StringIndexOutOfBoundsException.class, () -> new TextStringBuilder().deleteCharAt(-1258));
     }
 
     @Test
@@ -841,7 +839,7 @@ public class TextStringBuilderTest {
         final char[] b = new char[5];
         sb.set(data);
         assertEquals(2, sb.drainChars(0, 2, b, 3));
-        assertArrayEquals(new char[] {0, 0, 0, 'j', 'u'}, b);
+        assertArrayEquals(new char[] { 0, 0, 0, 'j', 'u' }, b);
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.drainChars(-1, 0, b, 0));
         assertThrows(IndexOutOfBoundsException.class, () -> sb.drainChars(0, -1, array, 0));
@@ -970,21 +968,16 @@ public class TextStringBuilderTest {
         assertTrue(sb1.equalsIgnoreCase(sb2));
 
         final Locale turkish = Locale.forLanguageTag("tr");
-        assertTrue(
-            new TextStringBuilder("title").equalsIgnoreCase(new TextStringBuilder("title".toLowerCase(turkish))));
-        assertTrue(
-            new TextStringBuilder("title").equalsIgnoreCase(new TextStringBuilder("TITLE".toLowerCase(turkish))));
-        assertTrue(
-            new TextStringBuilder("TITLE").equalsIgnoreCase(new TextStringBuilder("TITLE".toLowerCase(turkish))));
-        assertTrue(
-            new TextStringBuilder("TITLE").equalsIgnoreCase(new TextStringBuilder("title".toLowerCase(turkish))));
+        assertTrue(new TextStringBuilder("title").equalsIgnoreCase(new TextStringBuilder("title".toLowerCase(turkish))));
+        assertTrue(new TextStringBuilder("title").equalsIgnoreCase(new TextStringBuilder("TITLE".toLowerCase(turkish))));
+        assertTrue(new TextStringBuilder("TITLE").equalsIgnoreCase(new TextStringBuilder("TITLE".toLowerCase(turkish))));
+        assertTrue(new TextStringBuilder("TITLE").equalsIgnoreCase(new TextStringBuilder("title".toLowerCase(turkish))));
         //
         // assertTrue(new TextStringBuilder("title").equalsIgnoreCase(new
         // TextStringBuilder("title".toUpperCase(turkish))));
         // assertTrue(new TextStringBuilder("title").equalsIgnoreCase(new
         // TextStringBuilder("TITLE".toUpperCase(turkish))));
-        assertTrue(
-            new TextStringBuilder("TITLE").equalsIgnoreCase(new TextStringBuilder("TITLE".toUpperCase(turkish))));
+        assertTrue(new TextStringBuilder("TITLE").equalsIgnoreCase(new TextStringBuilder("TITLE".toUpperCase(turkish))));
         // assertTrue(new TextStringBuilder("TITLE").equalsIgnoreCase(new
         // TextStringBuilder("title".toUpperCase(turkish))));
     }
@@ -1001,7 +994,7 @@ public class TextStringBuilderTest {
         sb.append("junit");
         a = sb.getChars(input);
         assertSame(input, a);
-        assertArrayEquals(new char[] {'j', 'u', 'n', 'i', 't', 0, 0, 0, 0, 0}, a);
+        assertArrayEquals(new char[] { 'j', 'u', 'n', 'i', 't', 0, 0, 0, 0, 0 }, a);
 
         a = sb.getChars(null);
         assertNotSame(input, a);
@@ -1027,15 +1020,15 @@ public class TextStringBuilderTest {
 
         sb.set("junit");
         sb.getChars(0, 1, array1, 0);
-        assertArrayEquals(new char[] {'j'}, array1);
+        assertArrayEquals(new char[] { 'j' }, array1);
 
         final char[] array = new char[5];
         sb.getChars(0, 5, array, 0);
-        assertArrayEquals(new char[] {'j', 'u', 'n', 'i', 't'}, array);
+        assertArrayEquals(new char[] { 'j', 'u', 'n', 'i', 't' }, array);
 
         final char[] b = new char[5];
         sb.getChars(0, 2, b, 3);
-        assertArrayEquals(new char[] {0, 0, 0, 'j', 'u'}, b);
+        assertArrayEquals(new char[] { 0, 0, 0, 'j', 'u' }, b);
 
         assertThrows(IndexOutOfBoundsException.class, () -> sb.getChars(-1, 0, b, 0));
         assertThrows(IndexOutOfBoundsException.class, () -> sb.getChars(0, -1, array, 0));
@@ -1852,8 +1845,7 @@ public class TextStringBuilderTest {
         assertEquals("-x--y-", sb.toString());
 
         final TextStringBuilder builder = new TextStringBuilder("aaxaaaayaa");
-        assertThrows(IndexOutOfBoundsException.class,
-            () -> builder.replace(StringMatcherFactory.INSTANCE.stringMatcher("aa"), "-", 2, 1, -1));
+        assertThrows(IndexOutOfBoundsException.class, () -> builder.replace(StringMatcherFactory.INSTANCE.stringMatcher("aa"), "-", 2, 1, -1));
         assertEquals("aaxaaaayaa", builder.toString());
     }
 
@@ -1948,13 +1940,11 @@ public class TextStringBuilderTest {
         assertEquals("aaxaaaayaa", sb.toString());
 
         final TextStringBuilder builder = new TextStringBuilder("aaxaaaayaa");
-        assertThrows(IndexOutOfBoundsException.class,
-            () -> builder.replace(StringMatcherFactory.INSTANCE.stringMatcher("aa"), "-", 11, builder.length(), -1));
+        assertThrows(IndexOutOfBoundsException.class, () -> builder.replace(StringMatcherFactory.INSTANCE.stringMatcher("aa"), "-", 11, builder.length(), -1));
         assertEquals("aaxaaaayaa", builder.toString());
 
         builder.set("aaxaaaayaa");
-        assertThrows(IndexOutOfBoundsException.class,
-            () -> builder.replace(StringMatcherFactory.INSTANCE.stringMatcher("aa"), "-", -1, builder.length(), -1));
+        assertThrows(IndexOutOfBoundsException.class, () -> builder.replace(StringMatcherFactory.INSTANCE.stringMatcher("aa"), "-", -1, builder.length(), -1));
         assertEquals("aaxaaaayaa", builder.toString());
     }
 
diff --git a/src/test/java/org/apache/commons/text/WordUtilsTest.java b/src/test/java/org/apache/commons/text/WordUtilsTest.java
index bb3c95df..eaae3ca7 100644
--- a/src/test/java/org/apache/commons/text/WordUtilsTest.java
+++ b/src/test/java/org/apache/commons/text/WordUtilsTest.java
@@ -16,10 +16,11 @@
  */
 package org.apache.commons.text;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.lang.reflect.Constructor;
@@ -40,81 +41,81 @@ public class WordUtilsTest {
 
     @Test
     public void testAbbreviateForLowerThanMinusOneValues() {
-        assertThatIllegalArgumentException().isThrownBy(() -> assertThat(WordUtils.abbreviate("01 23 45 67 89", 9, -10, null)).isEqualTo("01 23 45 67"));
+        assertThrows(IllegalArgumentException.class, () -> WordUtils.abbreviate("01 23 45 67 89", 9, -10, null));
     }
 
-     @Test
+    @Test
     public void testAbbreviateForLowerValue() {
-        assertThat(WordUtils.abbreviate("012 3456789", 0, 5, null)).isEqualTo("012");
-        assertThat(WordUtils.abbreviate("01234 56789", 5, 10, null)).isEqualTo("01234");
-        assertThat(WordUtils.abbreviate("01 23 45 67 89", 9, -1, null)).isEqualTo("01 23 45 67");
-        assertThat(WordUtils.abbreviate("01 23 45 67 89", 9, 10, null)).isEqualTo("01 23 45 6");
-        assertThat(WordUtils.abbreviate("0123456789", 15, 20, null)).isEqualTo("0123456789");
+        assertEquals("012", WordUtils.abbreviate("012 3456789", 0, 5, null));
+        assertEquals("01234", WordUtils.abbreviate("01234 56789", 5, 10, null));
+        assertEquals("01 23 45 67", WordUtils.abbreviate("01 23 45 67 89", 9, -1, null));
+        assertEquals("01 23 45 6", WordUtils.abbreviate("01 23 45 67 89", 9, 10, null));
+        assertEquals("0123456789", WordUtils.abbreviate("0123456789", 15, 20, null));
     }
 
-     @Test
+    @Test
     public void testAbbreviateForLowerValueAndAppendedString() {
-        assertThat(WordUtils.abbreviate("012 3456789", 0, 5, null)).isEqualTo("012");
-        assertThat(WordUtils.abbreviate("01234 56789", 5, 10, "-")).isEqualTo("01234-");
-        assertThat(WordUtils.abbreviate("01 23 45 67 89", 9, -1, "abc")).isEqualTo("01 23 45 67abc");
-        assertThat(WordUtils.abbreviate("01 23 45 67 89", 9, 10, "")).isEqualTo("01 23 45 6");
+        assertEquals("012", WordUtils.abbreviate("012 3456789", 0, 5, null));
+        assertEquals("01234-", WordUtils.abbreviate("01234 56789", 5, 10, "-"));
+        assertEquals("01 23 45 67abc", WordUtils.abbreviate("01 23 45 67 89", 9, -1, "abc"));
+        assertEquals("01 23 45 6", WordUtils.abbreviate("01 23 45 67 89", 9, 10, ""));
     }
 
-     @Test
+    @Test
     public void testAbbreviateForNullAndEmptyString() {
-        assertThat(WordUtils.abbreviate(null, 1, -1, "")).isNull();
-        assertThat(WordUtils.abbreviate("", 1, -1, "")).isEqualTo(StringUtils.EMPTY);
-        assertThat(WordUtils.abbreviate("0123456790", 0, 0, "")).isEqualTo("");
-        assertThat(WordUtils.abbreviate(" 0123456790", 0, -1, "")).isEqualTo("");
+        assertNull(WordUtils.abbreviate(null, 1, -1, ""));
+        assertEquals(StringUtils.EMPTY, WordUtils.abbreviate("", 1, -1, ""));
+        assertEquals("", WordUtils.abbreviate("0123456790", 0, 0, ""));
+        assertEquals("", WordUtils.abbreviate(" 0123456790", 0, -1, ""));
     }
 
-     @Test
+    @Test
     public void testAbbreviateForUpperLimit() {
-        assertThat(WordUtils.abbreviate("0123456789", 0, 5, "")).isEqualTo("01234");
-        assertThat(WordUtils.abbreviate("012 3456789", 2, 5, "")).isEqualTo("012");
-        assertThat(WordUtils.abbreviate("0123456789", 0, -1, "")).isEqualTo("0123456789");
+        assertEquals("01234", WordUtils.abbreviate("0123456789", 0, 5, ""));
+        assertEquals("012", WordUtils.abbreviate("012 3456789", 2, 5, ""));
+        assertEquals("0123456789", WordUtils.abbreviate("0123456789", 0, -1, ""));
     }
 
-     @Test
+    @Test
     public void testAbbreviateForUpperLimitAndAppendedString() {
-        assertThat(WordUtils.abbreviate("0123456789", 0, 5, "-")).isEqualTo("01234-");
-        assertThat(WordUtils.abbreviate("012 3456789", 2, 5, null)).isEqualTo("012");
-        assertThat(WordUtils.abbreviate("0123456789", 0, -1, "")).isEqualTo("0123456789");
+        assertEquals("01234-", WordUtils.abbreviate("0123456789", 0, 5, "-"));
+        assertEquals("012", WordUtils.abbreviate("012 3456789", 2, 5, null));
+        assertEquals("0123456789", WordUtils.abbreviate("0123456789", 0, -1, ""));
     }
 
     @Test
     public void testAbbreviateUpperLessThanLowerValues() {
-        assertThatIllegalArgumentException().isThrownBy(() -> assertThat(WordUtils.abbreviate("0123456789", 5, 2, "")).isEqualTo("01234"));
+        assertThrows(IllegalArgumentException.class, () -> WordUtils.abbreviate("0123456789", 5, 2, ""));
     }
 
-     @Test
+    @Test
     public void testCapitalize_String() {
-        assertThat(WordUtils.capitalize(null)).isNull();
-        assertThat(WordUtils.capitalize("")).isEqualTo("");
-        assertThat(WordUtils.capitalize("  ")).isEqualTo("  ");
+        assertNull(WordUtils.capitalize(null));
+        assertEquals("", WordUtils.capitalize(""));
+        assertEquals("  ", WordUtils.capitalize("  "));
 
-        assertThat(WordUtils.capitalize("I")).isEqualTo("I");
-        assertThat(WordUtils.capitalize("i")).isEqualTo("I");
-        assertThat(WordUtils.capitalize("i am here 123")).isEqualTo("I Am Here 123");
-        assertThat(WordUtils.capitalize("I Am Here 123")).isEqualTo("I Am Here 123");
-        assertThat(WordUtils.capitalize("i am HERE 123")).isEqualTo("I Am HERE 123");
-        assertThat(WordUtils.capitalize("I AM HERE 123")).isEqualTo("I AM HERE 123");
+        assertEquals("I", WordUtils.capitalize("I"));
+        assertEquals("I", WordUtils.capitalize("i"));
+        assertEquals("I Am Here 123", WordUtils.capitalize("i am here 123"));
+        assertEquals("I Am Here 123", WordUtils.capitalize("I Am Here 123"));
+        assertEquals("I Am HERE 123", WordUtils.capitalize("i am HERE 123"));
+        assertEquals("I AM HERE 123", WordUtils.capitalize("I AM HERE 123"));
     }
 
     @Test
     public void testCapitalizeFully_String() {
-        assertThat(WordUtils.capitalizeFully(null)).isNull();
-        assertThat(WordUtils.capitalizeFully("")).isEqualTo("");
-        assertThat(WordUtils.capitalizeFully("  ")).isEqualTo("  ");
-        assertThat(WordUtils.capitalizeFully("I")).isEqualTo("I");
-        assertThat(WordUtils.capitalizeFully("i")).isEqualTo("I");
-        assertThat(WordUtils.capitalizeFully("i am here 123")).isEqualTo("I Am Here 123");
-        assertThat(WordUtils.capitalizeFully("I Am Here 123")).isEqualTo("I Am Here 123");
-        assertThat(WordUtils.capitalizeFully("i am HERE 123")).isEqualTo("I Am Here 123");
-        assertThat(WordUtils.capitalizeFully("I AM HERE 123")).isEqualTo("I Am Here 123");
-        assertThat(WordUtils.capitalizeFully("alphabet")).isEqualTo("Alphabet"); // single word
-        assertThat(WordUtils.capitalizeFully("a\tb\nc d")).isEqualTo("A\tB\nC D");
-        assertThat(WordUtils.capitalizeFully("and \tbut \ncleat  dome")).isEqualTo("And \tBut \nCleat  Dome");
+        assertNull(WordUtils.capitalizeFully(null));
+        assertEquals("", WordUtils.capitalizeFully(""));
+        assertEquals("  ", WordUtils.capitalizeFully("  "));
+        assertEquals("I", WordUtils.capitalizeFully("I"));
+        assertEquals("I", WordUtils.capitalizeFully("i"));
+        assertEquals("I Am Here 123", WordUtils.capitalizeFully("i am here 123"));
+        assertEquals("I Am Here 123", WordUtils.capitalizeFully("I Am Here 123"));
+        assertEquals("I Am Here 123", WordUtils.capitalizeFully("i am HERE 123"));
+        assertEquals("I Am Here 123", WordUtils.capitalizeFully("I AM HERE 123"));
+        assertEquals("Alphabet", WordUtils.capitalizeFully("alphabet")); // single word
+        assertEquals("A\tB\nC D", WordUtils.capitalizeFully("a\tb\nc d"));
+        assertEquals("And \tBut \nCleat  Dome", WordUtils.capitalizeFully("and \tbut \ncleat  dome"));
         // All whitespace
         assertEquals(WHITESPACE, WordUtils.capitalizeFully(WHITESPACE));
         assertEquals("A" + WHITESPACE + "B", WordUtils.capitalizeFully("a" + WHITESPACE + "b"));
@@ -123,55 +124,55 @@ public class WordUtilsTest {
 
     @Test
     public void testCapitalizeFully_Text88() {
-        assertThat(WordUtils.capitalizeFully("i am fine now", new char[] {})).isEqualTo("I am fine now");
+        assertEquals("I am fine now", WordUtils.capitalizeFully("i am fine now", new char[] {}));
     }
 
     @Test
     public void testCapitalizeFullyWithDelimiters_String() {
-        assertThat(WordUtils.capitalizeFully(null, null)).isNull();
-        assertThat(WordUtils.capitalizeFully("", ArrayUtils.EMPTY_CHAR_ARRAY)).isEqualTo("");
-        assertThat(WordUtils.capitalizeFully("  ", ArrayUtils.EMPTY_CHAR_ARRAY)).isEqualTo("  ");
-
-        char[] chars = {'-', '+', ' ', '@'};
-        assertThat(WordUtils.capitalizeFully("I", chars)).isEqualTo("I");
-        assertThat(WordUtils.capitalizeFully("i", chars)).isEqualTo("I");
-        assertThat(WordUtils.capitalizeFully("i-am here+123", chars)).isEqualTo("I-Am Here+123");
-        assertThat(WordUtils.capitalizeFully("I Am+Here-123", chars)).isEqualTo("I Am+Here-123");
-        assertThat(WordUtils.capitalizeFully("i+am-HERE 123", chars)).isEqualTo("I+Am-Here 123");
-        assertThat(WordUtils.capitalizeFully("I-AM HERE+123", chars)).isEqualTo("I-Am Here+123");
-        chars = new char[] {'.'};
-        assertThat(WordUtils.capitalizeFully("i aM.fine", chars)).isEqualTo("I am.Fine");
-        assertThat(WordUtils.capitalizeFully("i am.fine", null)).isEqualTo("I Am.fine");
-        assertThat(WordUtils.capitalizeFully("alphabet", null)).isEqualTo("Alphabet"); // single word
-        assertThat(WordUtils.capitalizeFully("alphabet", new char[] {'!'})).isEqualTo("Alphabet"); // no matching delim
+        assertNull(WordUtils.capitalizeFully(null, null));
+        assertEquals("", WordUtils.capitalizeFully("", ArrayUtils.EMPTY_CHAR_ARRAY));
+        assertEquals("  ", WordUtils.capitalizeFully("  ", ArrayUtils.EMPTY_CHAR_ARRAY));
+
+        char[] chars = { '-', '+', ' ', '@' };
+        assertEquals("I", WordUtils.capitalizeFully("I", chars));
+        assertEquals("I", WordUtils.capitalizeFully("i", chars));
+        assertEquals("I-Am Here+123", WordUtils.capitalizeFully("i-am here+123", chars));
+        assertEquals("I Am+Here-123", WordUtils.capitalizeFully("I Am+Here-123", chars));
+        assertEquals("I+Am-Here 123", WordUtils.capitalizeFully("i+am-HERE 123", chars));
+        assertEquals("I-Am Here+123", WordUtils.capitalizeFully("I-AM HERE+123", chars));
+        chars = new char[] { '.' };
+        assertEquals("I am.Fine", WordUtils.capitalizeFully("i aM.fine", chars));
+        assertEquals("I Am.fine", WordUtils.capitalizeFully("i am.fine", null));
+        assertEquals("Alphabet", WordUtils.capitalizeFully("alphabet", null)); // single word
+        assertEquals("Alphabet", WordUtils.capitalizeFully("alphabet", new char[] { '!' })); // no matching delim
     }
 
     @Test
     public void testCapitalizeWithDelimiters_String() {
-        assertThat(WordUtils.capitalize(null, null)).isNull();
-        assertThat(WordUtils.capitalize("", ArrayUtils.EMPTY_CHAR_ARRAY)).isEqualTo("");
-        assertThat(WordUtils.capitalize("  ", ArrayUtils.EMPTY_CHAR_ARRAY)).isEqualTo("  ");
-
-        char[] chars = {'-', '+', ' ', '@'};
-        assertThat(WordUtils.capitalize("I", chars)).isEqualTo("I");
-        assertThat(WordUtils.capitalize("i", chars)).isEqualTo("I");
-        assertThat(WordUtils.capitalize("i-am here+123", chars)).isEqualTo("I-Am Here+123");
-        assertThat(WordUtils.capitalize("I Am+Here-123", chars)).isEqualTo("I Am+Here-123");
-        assertThat(WordUtils.capitalize("i+am-HERE 123", chars)).isEqualTo("I+Am-HERE 123");
-        assertThat(WordUtils.capitalize("I-AM HERE+123", chars)).isEqualTo("I-AM HERE+123");
-        chars = new char[] {'.'};
-        assertThat(WordUtils.capitalize("i aM.fine", chars)).isEqualTo("I aM.Fine");
-        assertThat(WordUtils.capitalize("i am.fine", null)).isEqualTo("I Am.fine");
-    }
-
-     @Test
+        assertNull(WordUtils.capitalize(null, null));
+        assertEquals("", WordUtils.capitalize("", ArrayUtils.EMPTY_CHAR_ARRAY));
+        assertEquals("  ", WordUtils.capitalize("  ", ArrayUtils.EMPTY_CHAR_ARRAY));
+
+        char[] chars = { '-', '+', ' ', '@' };
+        assertEquals("I", WordUtils.capitalize("I", chars));
+        assertEquals("I", WordUtils.capitalize("i", chars));
+        assertEquals("I-Am Here+123", WordUtils.capitalize("i-am here+123", chars));
+        assertEquals("I Am+Here-123", WordUtils.capitalize("I Am+Here-123", chars));
+        assertEquals("I+Am-HERE 123", WordUtils.capitalize("i+am-HERE 123", chars));
+        assertEquals("I-AM HERE+123", WordUtils.capitalize("I-AM HERE+123", chars));
+        chars = new char[] { '.' };
+        assertEquals("I aM.Fine", WordUtils.capitalize("i aM.fine", chars));
+        assertEquals("I Am.fine", WordUtils.capitalize("i am.fine", null));
+    }
+
+    @Test
     public void testConstructor() {
-        assertThat(new WordUtils()).isNotNull();
+        assertNotNull(new WordUtils());
         final Constructor<?>[] cons = WordUtils.class.getDeclaredConstructors();
-        assertThat(cons.length).isEqualTo(1);
-        assertThat(Modifier.isPublic(cons[0].getModifiers())).isTrue();
-        assertThat(Modifier.isPublic(WordUtils.class.getModifiers())).isTrue();
-        assertThat(Modifier.isFinal(WordUtils.class.getModifiers())).isFalse();
+        assertEquals(1, cons.length);
+        assertTrue(Modifier.isPublic(cons[0].getModifiers()));
+        assertTrue(Modifier.isPublic(WordUtils.class.getModifiers()));
+        assertFalse(Modifier.isFinal(WordUtils.class.getModifiers()));
     }
 
     @Test
@@ -200,185 +201,178 @@ public class WordUtilsTest {
 
     @Test
     public void testContainsAllWordsWithNull() {
-        assertThat(WordUtils.containsAllWords("M", (CharSequence) null)).isFalse();
+        assertFalse(WordUtils.containsAllWords("M", (CharSequence) null));
     }
 
-     @Test
+    @Test
     public void testInitials_String() {
-        assertThat(WordUtils.initials(null)).isNull();
-        assertThat(WordUtils.initials("")).isEqualTo("");
-        assertThat(WordUtils.initials("  ")).isEqualTo("");
+        assertNull(WordUtils.initials(null));
+        assertEquals("", WordUtils.initials(""));
+        assertEquals("", WordUtils.initials("  "));
 
-        assertThat(WordUtils.initials("I")).isEqualTo("I");
-        assertThat(WordUtils.initials("i")).isEqualTo("i");
-        assertThat(WordUtils.initials("Ben John Lee")).isEqualTo("BJL");
-        assertThat(WordUtils.initials("   Ben \n   John\tLee\t")).isEqualTo("BJL");
-        assertThat(WordUtils.initials("Ben J.Lee")).isEqualTo("BJ");
-        assertThat(WordUtils.initials(" Ben   John  . Lee")).isEqualTo("BJ.L");
-        assertThat(WordUtils.initials("i am here 123")).isEqualTo("iah1");
+        assertEquals("I", WordUtils.initials("I"));
+        assertEquals("i", WordUtils.initials("i"));
+        assertEquals("BJL", WordUtils.initials("Ben John Lee"));
+        assertEquals("BJL", WordUtils.initials("   Ben \n   John\tLee\t"));
+        assertEquals("BJ", WordUtils.initials("Ben J.Lee"));
+        assertEquals("BJ.L", WordUtils.initials(" Ben   John  . Lee"));
+        assertEquals("iah1", WordUtils.initials("i am here 123"));
     }
 
-     @Test
+    @Test
     public void testInitials_String_charArray() {
         char[] array = null;
-        assertThat(WordUtils.initials(null, array)).isNull();
-        assertThat(WordUtils.initials("", array)).isEqualTo("");
-        assertThat(WordUtils.initials("  ", array)).isEqualTo("");
-        assertThat(WordUtils.initials("I", array)).isEqualTo("I");
-        assertThat(WordUtils.initials("i", array)).isEqualTo("i");
-        assertThat(WordUtils.initials("SJC", array)).isEqualTo("S");
-        assertThat(WordUtils.initials("Ben John Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials("   Ben \n   John\tLee\t", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials("Ben J.Lee", array)).isEqualTo("BJ");
-        assertThat(WordUtils.initials(" Ben   John  . Lee", array)).isEqualTo("BJ.L");
-        assertThat(WordUtils.initials("Kay O'Murphy", array)).isEqualTo("KO");
-        assertThat(WordUtils.initials("i am here 123", array)).isEqualTo("iah1");
+        assertNull(WordUtils.initials(null, array));
+        assertEquals("", WordUtils.initials("", array));
+        assertEquals("", WordUtils.initials("  ", array));
+        assertEquals("I", WordUtils.initials("I", array));
+        assertEquals("i", WordUtils.initials("i", array));
+        assertEquals("S", WordUtils.initials("SJC", array));
+        assertEquals("BJL", WordUtils.initials("Ben John Lee", array));
+        assertEquals("BJL", WordUtils.initials("   Ben \n   John\tLee\t", array));
+        assertEquals("BJ", WordUtils.initials("Ben J.Lee", array));
+        assertEquals("BJ.L", WordUtils.initials(" Ben   John  . Lee", array));
+        assertEquals("KO", WordUtils.initials("Kay O'Murphy", array));
+        assertEquals("iah1", WordUtils.initials("i am here 123", array));
 
         array = ArrayUtils.EMPTY_CHAR_ARRAY;
-        assertThat(WordUtils.initials(null, array)).isNull();
-        assertThat(WordUtils.initials("", array)).isEqualTo("");
-        assertThat(WordUtils.initials("  ", array)).isEqualTo("");
-        assertThat(WordUtils.initials("I", array)).isEqualTo("");
-        assertThat(WordUtils.initials("i", array)).isEqualTo("");
-        assertThat(WordUtils.initials("SJC", array)).isEqualTo("");
-        assertThat(WordUtils.initials("Ben John Lee", array)).isEqualTo("");
-        assertThat(WordUtils.initials("   Ben \n   John\tLee\t", array)).isEqualTo("");
-        assertThat(WordUtils.initials("Ben J.Lee", array)).isEqualTo("");
-        assertThat(WordUtils.initials(" Ben   John  . Lee", array)).isEqualTo("");
-        assertThat(WordUtils.initials("Kay O'Murphy", array)).isEqualTo("");
-        assertThat(WordUtils.initials("i am here 123", array)).isEqualTo("");
+        assertNull(WordUtils.initials(null, array));
+        assertEquals("", WordUtils.initials("", array));
+        assertEquals("", WordUtils.initials("  ", array));
+        assertEquals("", WordUtils.initials("I", array));
+        assertEquals("", WordUtils.initials("i", array));
+        assertEquals("", WordUtils.initials("SJC", array));
+        assertEquals("", WordUtils.initials("Ben John Lee", array));
+        assertEquals("", WordUtils.initials("   Ben \n   John\tLee\t", array));
+        assertEquals("", WordUtils.initials("Ben J.Lee", array));
+        assertEquals("", WordUtils.initials(" Ben   John  . Lee", array));
+        assertEquals("", WordUtils.initials("Kay O'Murphy", array));
+        assertEquals("", WordUtils.initials("i am here 123", array));
 
         array = " ".toCharArray();
-        assertThat(WordUtils.initials(null, array)).isNull();
-        assertThat(WordUtils.initials("", array)).isEqualTo("");
-        assertThat(WordUtils.initials("  ", array)).isEqualTo("");
-        assertThat(WordUtils.initials("I", array)).isEqualTo("I");
-        assertThat(WordUtils.initials("i", array)).isEqualTo("i");
-        assertThat(WordUtils.initials("SJC", array)).isEqualTo("S");
-        assertThat(WordUtils.initials("Ben John Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials("Ben J.Lee", array)).isEqualTo("BJ");
-        assertThat(WordUtils.initials("   Ben \n   John\tLee\t", array)).isEqualTo("B\nJ");
-        assertThat(WordUtils.initials(" Ben   John  . Lee", array)).isEqualTo("BJ.L");
-        assertThat(WordUtils.initials("Kay O'Murphy", array)).isEqualTo("KO");
-        assertThat(WordUtils.initials("i am here 123", array)).isEqualTo("iah1");
+        assertNull(WordUtils.initials(null, array));
+        assertEquals("", WordUtils.initials("", array));
+        assertEquals("", WordUtils.initials("  ", array));
+        assertEquals("I", WordUtils.initials("I", array));
+        assertEquals("i", WordUtils.initials("i", array));
+        assertEquals("S", WordUtils.initials("SJC", array));
+        assertEquals("BJL", WordUtils.initials("Ben John Lee", array));
+        assertEquals("BJ", WordUtils.initials("Ben J.Lee", array));
+        assertEquals("B\nJ", WordUtils.initials("   Ben \n   John\tLee\t", array));
+        assertEquals("BJ.L", WordUtils.initials(" Ben   John  . Lee", array));
+        assertEquals("KO", WordUtils.initials("Kay O'Murphy", array));
+        assertEquals("iah1", WordUtils.initials("i am here 123", array));
 
         array = " .".toCharArray();
-        assertThat(WordUtils.initials(null, array)).isNull();
-        assertThat(WordUtils.initials("", array)).isEqualTo("");
-        assertThat(WordUtils.initials("  ", array)).isEqualTo("");
-        assertThat(WordUtils.initials("I", array)).isEqualTo("I");
-        assertThat(WordUtils.initials("i", array)).isEqualTo("i");
-        assertThat(WordUtils.initials("SJC", array)).isEqualTo("S");
-        assertThat(WordUtils.initials("Ben John Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials("Ben J.Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials(" Ben   John  . Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials("Kay O'Murphy", array)).isEqualTo("KO");
-        assertThat(WordUtils.initials("i am here 123", array)).isEqualTo("iah1");
+        assertNull(WordUtils.initials(null, array));
+        assertEquals("", WordUtils.initials("", array));
+        assertEquals("", WordUtils.initials("  ", array));
+        assertEquals("I", WordUtils.initials("I", array));
+        assertEquals("i", WordUtils.initials("i", array));
+        assertEquals("S", WordUtils.initials("SJC", array));
+        assertEquals("BJL", WordUtils.initials("Ben John Lee", array));
+        assertEquals("BJL", WordUtils.initials("Ben J.Lee", array));
+        assertEquals("BJL", WordUtils.initials(" Ben   John  . Lee", array));
+        assertEquals("KO", WordUtils.initials("Kay O'Murphy", array));
+        assertEquals("iah1", WordUtils.initials("i am here 123", array));
 
         array = " .'".toCharArray();
-        assertThat(WordUtils.initials(null, array)).isNull();
-        assertThat(WordUtils.initials("", array)).isEqualTo("");
-        assertThat(WordUtils.initials("  ", array)).isEqualTo("");
-        assertThat(WordUtils.initials("I", array)).isEqualTo("I");
-        assertThat(WordUtils.initials("i", array)).isEqualTo("i");
-        assertThat(WordUtils.initials("SJC", array)).isEqualTo("S");
-        assertThat(WordUtils.initials("Ben John Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials("Ben J.Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials(" Ben   John  . Lee", array)).isEqualTo("BJL");
-        assertThat(WordUtils.initials("Kay O'Murphy", array)).isEqualTo("KOM");
-        assertThat(WordUtils.initials("i am here 123", array)).isEqualTo("iah1");
+        assertNull(WordUtils.initials(null, array));
+        assertEquals("", WordUtils.initials("", array));
+        assertEquals("", WordUtils.initials("  ", array));
+        assertEquals("I", WordUtils.initials("I", array));
+        assertEquals("i", WordUtils.initials("i", array));
+        assertEquals("S", WordUtils.initials("SJC", array));
+        assertEquals("BJL", WordUtils.initials("Ben John Lee", array));
+        assertEquals("BJL", WordUtils.initials("Ben J.Lee", array));
+        assertEquals("BJL", WordUtils.initials(" Ben   John  . Lee", array));
+        assertEquals("KOM", WordUtils.initials("Kay O'Murphy", array));
+        assertEquals("iah1", WordUtils.initials("i am here 123", array));
 
         array = "SIJo1".toCharArray();
-        assertThat(WordUtils.initials(null, array)).isNull();
-        assertThat(WordUtils.initials("", array)).isEqualTo("");
-        assertThat(WordUtils.initials("  ", array)).isEqualTo(" ");
-        assertThat(WordUtils.initials("I", array)).isEqualTo("");
-        assertThat(WordUtils.initials("i", array)).isEqualTo("i");
-        assertThat(WordUtils.initials("SJC", array)).isEqualTo("C");
-        assertThat(WordUtils.initials("Ben John Lee", array)).isEqualTo("Bh");
-        assertThat(WordUtils.initials("Ben J.Lee", array)).isEqualTo("B.");
-        assertThat(WordUtils.initials(" Ben   John  . Lee", array)).isEqualTo(" h");
-        assertThat(WordUtils.initials("Kay O'Murphy", array)).isEqualTo("K");
-        assertThat(WordUtils.initials("i am here 123", array)).isEqualTo("i2");
+        assertNull(WordUtils.initials(null, array));
+        assertEquals("", WordUtils.initials("", array));
+        assertEquals(" ", WordUtils.initials("  ", array));
+        assertEquals("", WordUtils.initials("I", array));
+        assertEquals("i", WordUtils.initials("i", array));
+        assertEquals("C", WordUtils.initials("SJC", array));
+        assertEquals("Bh", WordUtils.initials("Ben John Lee", array));
+        assertEquals("B.", WordUtils.initials("Ben J.Lee", array));
+        assertEquals(" h", WordUtils.initials(" Ben   John  . Lee", array));
+        assertEquals("K", WordUtils.initials("Kay O'Murphy", array));
+        assertEquals("i2", WordUtils.initials("i am here 123", array));
     }
 
     @Test
     public void testInitialsSurrogatePairs() {
         // Tests with space as default delimiter
-        assertThat(WordUtils.initials("\uD800\uDF00\uD800\uDF01 \uD800\uDF02\uD800\uDF03"))
-            .isEqualTo("\uD800\uDF00\uD800\uDF02");
-        assertThat(WordUtils.initials("\uD800\uDF00\uD800\uDF01 \uD800\uDF02\uD800\uDF03", null))
-            .isEqualTo("\uD800\uDF00\uD800\uDF02");
-        assertThat(WordUtils.initials("\uD800\uDF00 \uD800\uDF02 ", null)).isEqualTo("\uD800\uDF00\uD800\uDF02");
+        assertEquals("\uD800\uDF00\uD800\uDF02", WordUtils.initials("\uD800\uDF00\uD800\uDF01 \uD800\uDF02\uD800\uDF03"));
+        assertEquals("\uD800\uDF00\uD800\uDF02", WordUtils.initials("\uD800\uDF00\uD800\uDF01 \uD800\uDF02\uD800\uDF03", null));
+        assertEquals("\uD800\uDF00\uD800\uDF02", WordUtils.initials("\uD800\uDF00 \uD800\uDF02 ", null));
 
         // Tests with UTF-16 as delimiters
-        assertThat(WordUtils.initials("\uD800\uDF00\uD800\uDF01.\uD800\uDF02\uD800\uDF03", new char[] {'.'}))
-            .isEqualTo("\uD800\uDF00\uD800\uDF02");
-        assertThat(WordUtils.initials("\uD800\uDF00\uD800\uDF01A\uD800\uDF02\uD800\uDF03", new char[] {'A'}))
-            .isEqualTo("\uD800\uDF00\uD800\uDF02");
+        assertEquals("\uD800\uDF00\uD800\uDF02", WordUtils.initials("\uD800\uDF00\uD800\uDF01.\uD800\uDF02\uD800\uDF03", new char[] { '.' }));
+        assertEquals("\uD800\uDF00\uD800\uDF02", WordUtils.initials("\uD800\uDF00\uD800\uDF01A\uD800\uDF02\uD800\uDF03", new char[] { 'A' }));
 
         // Tests with UTF-32 as delimiters
-        assertThat(WordUtils.initials(
-                "\uD800\uDF00\uD800\uDF01\uD800\uDF14\uD800\uDF02\uD800\uDF03", new char[] {'\uD800', '\uDF14'}))
-            .isEqualTo("\uD800\uDF00\uD800\uDF02");
-        assertThat(WordUtils.initials("\uD800\uDF00\uD800\uDF01\uD800\uDF14\uD800\uDF18\uD800\uDF02\uD800\uDF03",
-                        new char[] {'\uD800', '\uDF14', '\uD800', '\uDF18'}))
-            .isEqualTo("\uD800\uDF00\uD800\uDF02");
+        assertEquals("\uD800\uDF00\uD800\uDF02",
+                WordUtils.initials("\uD800\uDF00\uD800\uDF01\uD800\uDF14\uD800\uDF02\uD800\uDF03", new char[] { '\uD800', '\uDF14' }));
+        assertEquals("\uD800\uDF00\uD800\uDF02", WordUtils.initials("\uD800\uDF00\uD800\uDF01\uD800\uDF14\uD800\uDF18\uD800\uDF02\uD800\uDF03",
+                new char[] { '\uD800', '\uDF14', '\uD800', '\uDF18' }));
     }
 
     @Test
     public void testLANG1292() {
         // Prior to fix, this was throwing StringIndexOutOfBoundsException
-        WordUtils.wrap("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa "
-                + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa "
-                + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", 70);
+        WordUtils.wrap("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa " + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa " + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+                70);
     }
 
     @Test
     public void testLANG673() {
-        assertThat(WordUtils.abbreviate("01 23 45 67 89", 0, 40, "")).isEqualTo("01");
-        assertThat(WordUtils.abbreviate("01 23 45 67 89", 10, 40, "")).isEqualTo("01 23 45 67");
-        assertThat(WordUtils.abbreviate("01 23 45 67 89", 40, 40, "")).isEqualTo("01 23 45 67 89");
+        assertEquals("01", WordUtils.abbreviate("01 23 45 67 89", 0, 40, ""));
+        assertEquals("01 23 45 67", WordUtils.abbreviate("01 23 45 67 89", 10, 40, ""));
+        assertEquals("01 23 45 67 89", WordUtils.abbreviate("01 23 45 67 89", 40, 40, ""));
     }
 
-     @Test
+    @Test
     public void testSwapCase_String() {
-        assertThat(WordUtils.swapCase(null)).isNull();
-        assertThat(WordUtils.swapCase("")).isEqualTo("");
-        assertThat(WordUtils.swapCase("  ")).isEqualTo("  ");
+        assertNull(WordUtils.swapCase(null));
+        assertEquals("", WordUtils.swapCase(""));
+        assertEquals("  ", WordUtils.swapCase("  "));
 
-        assertThat(WordUtils.swapCase("I")).isEqualTo("i");
-        assertThat(WordUtils.swapCase("i")).isEqualTo("I");
-        assertThat(WordUtils.swapCase("i am here 123")).isEqualTo("I AM HERE 123");
-        assertThat(WordUtils.swapCase("I Am Here 123")).isEqualTo("i aM hERE 123");
-        assertThat(WordUtils.swapCase("i am HERE 123")).isEqualTo("I AM here 123");
-        assertThat(WordUtils.swapCase("I AM HERE 123")).isEqualTo("i am here 123");
+        assertEquals("i", WordUtils.swapCase("I"));
+        assertEquals("I", WordUtils.swapCase("i"));
+        assertEquals("I AM HERE 123", WordUtils.swapCase("i am here 123"));
+        assertEquals("i aM hERE 123", WordUtils.swapCase("I Am Here 123"));
+        assertEquals("I AM here 123", WordUtils.swapCase("i am HERE 123"));
+        assertEquals("i am here 123", WordUtils.swapCase("I AM HERE 123"));
 
         final String test = "This String contains a TitleCase character: \u01C8";
         final String expect = "tHIS sTRING CONTAINS A tITLEcASE CHARACTER: \u01C9";
-        assertThat(WordUtils.swapCase(test)).isEqualTo(expect);
+        assertEquals(expect, WordUtils.swapCase(test));
     }
 
     @Test
     public void testText123() throws Exception {
         // Prior to fix, this was throwing StringIndexOutOfBoundsException
-        WordUtils.wrap("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa "
-                + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", Integer.MAX_VALUE);
+        WordUtils.wrap("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa " + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+                Integer.MAX_VALUE);
     }
 
     @Test
     public void testUncapitalize_String() {
-        assertThat(WordUtils.uncapitalize(null)).isNull();
-        assertThat(WordUtils.uncapitalize("")).isEqualTo("");
-        assertThat(WordUtils.uncapitalize("  ")).isEqualTo("  ");
-        assertThat(WordUtils.uncapitalize("I")).isEqualTo("i");
-        assertThat(WordUtils.uncapitalize("i")).isEqualTo("i");
-        assertThat(WordUtils.uncapitalize("i am here 123")).isEqualTo("i am here 123");
-        assertThat(WordUtils.uncapitalize("I Am Here 123")).isEqualTo("i am here 123");
-        assertThat(WordUtils.uncapitalize("i am HERE 123")).isEqualTo("i am hERE 123");
-        assertThat(WordUtils.uncapitalize("I AM HERE 123")).isEqualTo("i aM hERE 123");
-        assertThat(WordUtils.uncapitalize("A\tB\nC D")).isEqualTo("a\tb\nc d");
-        assertThat(WordUtils.uncapitalize("And \tBut \nCLEAT  Dome")).isEqualTo("and \tbut \ncLEAT  dome");
+        assertNull(WordUtils.uncapitalize(null));
+        assertEquals("", WordUtils.uncapitalize(""));
+        assertEquals("  ", WordUtils.uncapitalize("  "));
+        assertEquals("i", WordUtils.uncapitalize("I"));
+        assertEquals("i", WordUtils.uncapitalize("i"));
+        assertEquals("i am here 123", WordUtils.uncapitalize("i am here 123"));
+        assertEquals("i am here 123", WordUtils.uncapitalize("I Am Here 123"));
+        assertEquals("i am hERE 123", WordUtils.uncapitalize("i am HERE 123"));
+        assertEquals("i aM hERE 123", WordUtils.uncapitalize("I AM HERE 123"));
+        assertEquals("a\tb\nc d", WordUtils.uncapitalize("A\tB\nC D"));
+        assertEquals("and \tbut \ncLEAT  dome", WordUtils.uncapitalize("And \tBut \nCLEAT  Dome"));
         // All whitespace
         assertEquals(WHITESPACE, WordUtils.capitalizeFully(WHITESPACE));
         assertEquals("A" + WHITESPACE + "B", WordUtils.capitalizeFully("a" + WHITESPACE + "b"));
@@ -386,136 +380,132 @@ public class WordUtilsTest {
 
     @Test
     public void testUnCapitalize_Text88() {
-        assertThat(WordUtils.uncapitalize("I am fine now", new char[] {})).isEqualTo("i am fine now");
+        assertEquals("i am fine now", WordUtils.uncapitalize("I am fine now", new char[] {}));
     }
 
     @Test
     public void testUncapitalizeWithDelimiters_String() {
-        assertThat(WordUtils.uncapitalize(null, null)).isNull();
-        assertThat(WordUtils.uncapitalize("", ArrayUtils.EMPTY_CHAR_ARRAY)).isEqualTo("");
-        assertThat(WordUtils.uncapitalize("  ", ArrayUtils.EMPTY_CHAR_ARRAY)).isEqualTo("  ");
-
-        char[] chars = {'-', '+', ' ', '@'};
-        assertThat(WordUtils.uncapitalize("I", chars)).isEqualTo("i");
-        assertThat(WordUtils.uncapitalize("i", chars)).isEqualTo("i");
-        assertThat(WordUtils.uncapitalize("i am-here+123", chars)).isEqualTo("i am-here+123");
-        assertThat(WordUtils.uncapitalize("I+Am Here-123", chars)).isEqualTo("i+am here-123");
-        assertThat(WordUtils.uncapitalize("i-am+HERE 123", chars)).isEqualTo("i-am+hERE 123");
-        assertThat(WordUtils.uncapitalize("I AM-HERE+123", chars)).isEqualTo("i aM-hERE+123");
-        chars = new char[] {'.'};
-        assertThat(WordUtils.uncapitalize("I AM.FINE", chars)).isEqualTo("i AM.fINE");
-        assertThat(WordUtils.uncapitalize("I AM.FINE", null)).isEqualTo("i aM.FINE");
-    }
-
-     @Test
+        assertNull(WordUtils.uncapitalize(null, null));
+        assertEquals("", WordUtils.uncapitalize("", ArrayUtils.EMPTY_CHAR_ARRAY));
+        assertEquals("  ", WordUtils.uncapitalize("  ", ArrayUtils.EMPTY_CHAR_ARRAY));
+
+        char[] chars = { '-', '+', ' ', '@' };
+        assertEquals("i", WordUtils.uncapitalize("I", chars));
+        assertEquals("i", WordUtils.uncapitalize("i", chars));
+        assertEquals("i am-here+123", WordUtils.uncapitalize("i am-here+123", chars));
+        assertEquals("i+am here-123", WordUtils.uncapitalize("I+Am Here-123", chars));
+        assertEquals("i-am+hERE 123", WordUtils.uncapitalize("i-am+HERE 123", chars));
+        assertEquals("i aM-hERE+123", WordUtils.uncapitalize("I AM-HERE+123", chars));
+        chars = new char[] { '.' };
+        assertEquals("i AM.fINE", WordUtils.uncapitalize("I AM.FINE", chars));
+        assertEquals("i aM.FINE", WordUtils.uncapitalize("I AM.FINE", null));
+    }
+
+    @Test
     public void testWrap_StringInt() {
-        assertThat(WordUtils.wrap(null, 20)).isNull();
-        assertThat(WordUtils.wrap(null, -1)).isNull();
+        assertNull(WordUtils.wrap(null, 20));
+        assertNull(WordUtils.wrap(null, -1));
 
-        assertThat(WordUtils.wrap("", 20)).isEqualTo("");
-        assertThat(WordUtils.wrap("", -1)).isEqualTo("");
+        assertEquals("", WordUtils.wrap("", 20));
+        assertEquals("", WordUtils.wrap("", -1));
 
         // normal
         final String systemNewLine = System.lineSeparator();
         String input = "Here is one line of text that is going to be wrapped after 20 columns.";
-        String expected = "Here is one line of" + systemNewLine + "text that is going" + systemNewLine
-                + "to be wrapped after" + systemNewLine + "20 columns.";
-        assertThat(WordUtils.wrap(input, 20)).isEqualTo(expected);
+        String expected = "Here is one line of" + systemNewLine + "text that is going" + systemNewLine + "to be wrapped after" + systemNewLine + "20 columns.";
+        assertEquals(expected, WordUtils.wrap(input, 20));
 
         // long word at end
         input = "Click here to jump to the commons website - https://commons.apache.org";
-        expected = "Click here to jump" + systemNewLine + "to the commons" + systemNewLine + "website -" + systemNewLine
-                + "https://commons.apache.org";
-        assertThat(WordUtils.wrap(input, 20)).isEqualTo(expected);
+        expected = "Click here to jump" + systemNewLine + "to the commons" + systemNewLine + "website -" + systemNewLine + "https://commons.apache.org";
+        assertEquals(expected, WordUtils.wrap(input, 20));
 
         // long word in middle
         input = "Click here, https://commons.apache.org, to jump to the commons website";
-        expected = "Click here," + systemNewLine + "https://commons.apache.org," + systemNewLine + "to jump to the"
-                + systemNewLine + "commons website";
-        assertThat(WordUtils.wrap(input, 20)).isEqualTo(expected);
+        expected = "Click here," + systemNewLine + "https://commons.apache.org," + systemNewLine + "to jump to the" + systemNewLine + "commons website";
+        assertEquals(expected, WordUtils.wrap(input, 20));
 
         // leading spaces on a new line are stripped
         // trailing spaces are not stripped
         input = "word1             word2                        word3";
         expected = "word1  " + systemNewLine + "word2  " + systemNewLine + "word3";
-        assertThat(WordUtils.wrap(input, 7)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 7));
     }
 
     @Test
     public void testWrap_StringIntStringBoolean() {
-        assertThat(WordUtils.wrap(null, 20, "\n", false)).isNull();
-        assertThat(WordUtils.wrap(null, 20, "\n", true)).isNull();
-        assertThat(WordUtils.wrap(null, 20, null, true)).isNull();
-        assertThat(WordUtils.wrap(null, 20, null, false)).isNull();
-        assertThat(WordUtils.wrap(null, -1, null, true)).isNull();
-        assertThat(WordUtils.wrap(null, -1, null, false)).isNull();
-
-        assertThat(WordUtils.wrap("", 20, "\n", false)).isEqualTo("");
-        assertThat(WordUtils.wrap("", 20, "\n", true)).isEqualTo("");
-        assertThat(WordUtils.wrap("", 20, null, false)).isEqualTo("");
-        assertThat(WordUtils.wrap("", 20, null, true)).isEqualTo("");
-        assertThat(WordUtils.wrap("", -1, null, false)).isEqualTo("");
-        assertThat(WordUtils.wrap("", -1, null, true)).isEqualTo("");
+        assertNull(WordUtils.wrap(null, 20, "\n", false));
+        assertNull(WordUtils.wrap(null, 20, "\n", true));
+        assertNull(WordUtils.wrap(null, 20, null, true));
+        assertNull(WordUtils.wrap(null, 20, null, false));
+        assertNull(WordUtils.wrap(null, -1, null, true));
+        assertNull(WordUtils.wrap(null, -1, null, false));
+
+        assertEquals("", WordUtils.wrap("", 20, "\n", false));
+        assertEquals("", WordUtils.wrap("", 20, "\n", true));
+        assertEquals("", WordUtils.wrap("", 20, null, false));
+        assertEquals("", WordUtils.wrap("", 20, null, true));
+        assertEquals("", WordUtils.wrap("", -1, null, false));
+        assertEquals("", WordUtils.wrap("", -1, null, true));
 
         // normal
         String input = "Here is one line of text that is going to be wrapped after 20 columns.";
         String expected = "Here is one line of\ntext that is going\nto be wrapped after\n20 columns.";
-        assertThat(WordUtils.wrap(input, 20, "\n", false)).isEqualTo(expected);
-        assertThat(WordUtils.wrap(input, 20, "\n", true)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", false));
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", true));
 
         // unusual newline char
         input = "Here is one line of text that is going to be wrapped after 20 columns.";
         expected = "Here is one line of<br />text that is going<br />to be wrapped after<br />20 columns.";
-        assertThat(WordUtils.wrap(input, 20, "<br />", false)).isEqualTo(expected);
-        assertThat(WordUtils.wrap(input, 20, "<br />", true)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "<br />", false));
+        assertEquals(expected, WordUtils.wrap(input, 20, "<br />", true));
 
         // short line length
         input = "Here is one line";
         expected = "Here\nis one\nline";
-        assertThat(WordUtils.wrap(input, 6, "\n", false)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 6, "\n", false));
         expected = "Here\nis\none\nline";
-        assertThat(WordUtils.wrap(input, 2, "\n", false)).isEqualTo(expected);
-        assertThat(WordUtils.wrap(input, -1, "\n", false)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 2, "\n", false));
+        assertEquals(expected, WordUtils.wrap(input, -1, "\n", false));
 
         // system newline char
         final String systemNewLine = System.lineSeparator();
         input = "Here is one line of text that is going to be wrapped after 20 columns.";
-        expected = "Here is one line of" + systemNewLine + "text that is going" + systemNewLine + "to be wrapped after"
-                + systemNewLine + "20 columns.";
-        assertThat(WordUtils.wrap(input, 20, null, false)).isEqualTo(expected);
-        assertThat(WordUtils.wrap(input, 20, null, true)).isEqualTo(expected);
+        expected = "Here is one line of" + systemNewLine + "text that is going" + systemNewLine + "to be wrapped after" + systemNewLine + "20 columns.";
+        assertEquals(expected, WordUtils.wrap(input, 20, null, false));
+        assertEquals(expected, WordUtils.wrap(input, 20, null, true));
 
         // with extra spaces
         input = " Here:  is  one  line  of  text  that  is  going  to  be  wrapped  after  20  columns.";
         expected = "Here:  is  one  line\nof  text  that  is \ngoing  to  be \nwrapped  after  20 \ncolumns.";
-        assertThat(WordUtils.wrap(input, 20, "\n", false)).isEqualTo(expected);
-        assertThat(WordUtils.wrap(input, 20, "\n", true)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", false));
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", true));
 
         // with tab
         input = "Here is\tone line of text that is going to be wrapped after 20 columns.";
         expected = "Here is\tone line of\ntext that is going\nto be wrapped after\n20 columns.";
-        assertThat(WordUtils.wrap(input, 20, "\n", false)).isEqualTo(expected);
-        assertThat(WordUtils.wrap(input, 20, "\n", true)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", false));
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", true));
 
         // with tab at wrapColumn
         input = "Here is one line of\ttext that is going to be wrapped after 20 columns.";
         expected = "Here is one line\nof\ttext that is\ngoing to be wrapped\nafter 20 columns.";
-        assertThat(WordUtils.wrap(input, 20, "\n", false)).isEqualTo(expected);
-        assertThat(WordUtils.wrap(input, 20, "\n", true)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", false));
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", true));
 
         // difference because of long word
         input = "Click here to jump to the commons website - https://commons.apache.org";
         expected = "Click here to jump\nto the commons\nwebsite -\nhttps://commons.apache.org";
-        assertThat(WordUtils.wrap(input, 20, "\n", false)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", false));
         expected = "Click here to jump\nto the commons\nwebsite -\nhttps://commons.apac\nhe.org";
-        assertThat(WordUtils.wrap(input, 20, "\n", true)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", true));
 
         // difference because of long word in middle
         input = "Click here, https://commons.apache.org, to jump to the commons website";
         expected = "Click here,\nhttps://commons.apache.org,\nto jump to the\ncommons website";
-        assertThat(WordUtils.wrap(input, 20, "\n", false)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", false));
         expected = "Click here,\nhttps://commons.apac\nhe.org, to jump to\nthe commons website";
-        assertThat(WordUtils.wrap(input, 20, "\n", true)).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 20, "\n", true));
     }
 
     @Test
@@ -524,44 +514,44 @@ public class WordUtilsTest {
         // no changes test
         String input = "flammable/inflammable";
         String expected = "flammable/inflammable";
-        assertThat(WordUtils.wrap(input, 30, "\n", false, "/")).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 30, "\n", false, "/"));
 
         // wrap on / and small width
         expected = "flammable\ninflammable";
-        assertThat(WordUtils.wrap(input, 2, "\n", false, "/")).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 2, "\n", false, "/"));
 
         // wrap long words on / 1
         expected = "flammable\ninflammab\nle";
-        assertThat(WordUtils.wrap(input, 9, "\n", true, "/")).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 9, "\n", true, "/"));
 
         // wrap long words on / 2
         expected = "flammable\ninflammable";
-        assertThat(WordUtils.wrap(input, 15, "\n", true, "/")).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 15, "\n", true, "/"));
 
         // wrap long words on / 3
         input = "flammableinflammable";
         expected = "flammableinflam\nmable";
-        assertThat(WordUtils.wrap(input, 15, "\n", true, "/")).isEqualTo(expected);
+        assertEquals(expected, WordUtils.wrap(input, 15, "\n", true, "/"));
     }
 
     @Test
     public void testWrapAtMiddleTwice() {
-        assertThat(WordUtils.wrap("abcdefggabcdef", 2, "\n", false, "(?=g)")).isEqualTo("abcdef\n\nabcdef");
+        assertEquals("abcdef\n\nabcdef", WordUtils.wrap("abcdefggabcdef", 2, "\n", false, "(?=g)"));
     }
 
     @Test
     public void testWrapAtStartAndEnd() {
-        assertThat(WordUtils.wrap("nabcdefabcdefn", 2, "\n", false, "(?=n)")).isEqualTo("\nabcdefabcdef\n");
+        assertEquals("\nabcdefabcdef\n", WordUtils.wrap("nabcdefabcdefn", 2, "\n", false, "(?=n)"));
     }
 
     @Test
     public void testWrapWithMultipleRegexMatchOfLength0() {
-        assertThat(WordUtils.wrap("abcdefabcdef", 2, "\n", false, "(?=d)")).isEqualTo("abc\ndefabc\ndef");
+        assertEquals("abc\ndefabc\ndef", WordUtils.wrap("abcdefabcdef", 2, "\n", false, "(?=d)"));
     }
 
     @Test
     public void testWrapWithRegexMatchOfLength0() {
-        assertThat(WordUtils.wrap("abcdef", 2, "\n", false, "(?=d)")).isEqualTo("abc\ndef");
+        assertEquals("abc\ndef", WordUtils.wrap("abcdef", 2, "\n", false, "(?=d)"));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/diff/ReplacementsFinderTest.java b/src/test/java/org/apache/commons/text/diff/ReplacementsFinderTest.java
index b9e24755..8491effd 100644
--- a/src/test/java/org/apache/commons/text/diff/ReplacementsFinderTest.java
+++ b/src/test/java/org/apache/commons/text/diff/ReplacementsFinderTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.diff;
 
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -86,7 +86,7 @@ public class ReplacementsFinderTest {
         final StringsComparator sc = new StringsComparator(left, right);
         final ReplacementsFinder<Character> replacementFinder = new ReplacementsFinder<>(handler);
         sc.getScript().visit(replacementFinder);
-        assertThat(handler.getSkipped()).as("Skipped characters do not match").isEqualTo(skipped);
+        assertEquals(skipped, handler.getSkipped(), "Skipped characters do not match");
         assertArrayEquals(handler.getFrom().toArray(ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY), from,
             "From characters do not match");
         assertArrayEquals(to, handler.getTo().toArray(ArrayUtils.EMPTY_CHARACTER_OBJECT_ARRAY),
diff --git a/src/test/java/org/apache/commons/text/diff/StringsComparatorTest.java b/src/test/java/org/apache/commons/text/diff/StringsComparatorTest.java
index 29326ce8..5a82945b 100644
--- a/src/test/java/org/apache/commons/text/diff/StringsComparatorTest.java
+++ b/src/test/java/org/apache/commons/text/diff/StringsComparatorTest.java
@@ -15,7 +15,8 @@
  * limitations under the License.
  */
 package org.apache.commons.text.diff;
-import static org.assertj.core.api.Assertions.assertThat;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.Arrays;
 import java.util.List;
@@ -118,7 +119,7 @@ public class StringsComparatorTest {
         for (int i = 0; i < before.size(); ++i) {
             final ExecutionVisitor<Character> ev = new ExecutionVisitor<>();
             new StringsComparator(before.get(i), after.get(i)).getScript().visit(ev);
-            assertThat(ev.getString()).isEqualTo(after.get(i));
+            assertEquals(after.get(i), ev.getString());
         }
     }
 
@@ -126,14 +127,14 @@ public class StringsComparatorTest {
     public void testLength() {
         for (int i = 0; i < before.size(); ++i) {
             final StringsComparator comparator =  new StringsComparator(before.get(i), after.get(i));
-            assertThat(comparator.getScript().getModifications()).isEqualTo(length[i]);
+            assertEquals(length[i], comparator.getScript().getModifications());
         }
     }
     @Test
     public void testLongestCommonSubsequence() {
         for (int i = 0; i < before.size(); ++i) {
             final StringsComparator comparator =  new StringsComparator(before.get(i), after.get(i));
-            assertThat(comparator.getScript().getLCSLength()).isEqualTo(lcs[i]);
+            assertEquals(lcs[i], comparator.getScript().getLCSLength());
         }
     }
 }
diff --git a/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharArrayTest.java b/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharArrayTest.java
index 70143010..1d982df2 100644
--- a/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharArrayTest.java
+++ b/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharArrayTest.java
@@ -16,8 +16,9 @@
  */
 package org.apache.commons.text.matcher;
 
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertSame;
 
 import org.junit.jupiter.api.Test;
 
@@ -33,31 +34,30 @@ public class StringMatcherOnCharArrayTest {
     private static final int INPUT2_LENGTH = INPUT2.length;
 
     private void checkAndMatcher_char(final StringMatcher matcher) {
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(3);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(3, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(3);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(3, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
     }
 
     @Test
     public void testAndMatcher_char() {
-        final StringMatcher matcher1 = StringMatcherFactory.INSTANCE.andMatcher(
-            StringMatcherFactory.INSTANCE.charMatcher('c'), StringMatcherFactory.INSTANCE.stringMatcher("de"));
+        final StringMatcher matcher1 = StringMatcherFactory.INSTANCE.andMatcher(StringMatcherFactory.INSTANCE.charMatcher('c'),
+                StringMatcherFactory.INSTANCE.stringMatcher("de"));
         assertEquals(3, matcher1.size());
         checkAndMatcher_char(matcher1);
         //
-        final StringMatcher matcher2 = StringMatcherFactory.INSTANCE.andMatcher(null,
-            StringMatcherFactory.INSTANCE.charMatcher('c'), null, StringMatcherFactory.INSTANCE.stringMatcher("de"),
-            null);
+        final StringMatcher matcher2 = StringMatcherFactory.INSTANCE.andMatcher(null, StringMatcherFactory.INSTANCE.charMatcher('c'), null,
+                StringMatcherFactory.INSTANCE.stringMatcher("de"), null);
         assertEquals(3, matcher2.size());
         checkAndMatcher_char(matcher2);
     }
@@ -67,19 +67,19 @@ public class StringMatcherOnCharArrayTest {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.charMatcher('c');
         assertEquals(1, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(1, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
     }
 
     @Test
@@ -87,26 +87,23 @@ public class StringMatcherOnCharArrayTest {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.charSetMatcher("ace".toCharArray());
         assertEquals(1, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(1, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(1, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
         //
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher())
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher((char[]) null))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE
-            .charSetMatcher("a".toCharArray()) instanceof AbstractStringMatcher.CharMatcher).isTrue();
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher(), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher((char[]) null), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertInstanceOf(AbstractStringMatcher.CharMatcher.class, StringMatcherFactory.INSTANCE.charSetMatcher("a".toCharArray()));
     }
 
     @Test
@@ -114,54 +111,51 @@ public class StringMatcherOnCharArrayTest {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.charSetMatcher("ace");
         assertEquals(1, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(1, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(1, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
         //
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher(""))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher((String) null))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher("a") instanceof AbstractStringMatcher.CharMatcher)
-            .isTrue();
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher(""), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher((String) null), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertInstanceOf(AbstractStringMatcher.CharMatcher.class, StringMatcherFactory.INSTANCE.charSetMatcher("a"));
     }
 
     @Test
     public void testCommaMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.commaMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.commaMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.commaMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 0, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 1, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0));
+        assertEquals(1, matcher.isMatch(INPUT1, 1));
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
     }
 
     @Test
     public void testDoubleQuoteMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.doubleQuoteMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.doubleQuoteMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.doubleQuoteMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 11, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 12, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 11));
+        assertEquals(1, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
@@ -171,145 +165,143 @@ public class StringMatcherOnCharArrayTest {
         // the concern of StringMatcher, and are not bugs
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.stringMatcher("bc");
         assertEquals(2, matcher.size());
-        assertThat(matcher.isMatch(INPUT2, 1, 1, INPUT2_LENGTH)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, 3)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, 2)).isEqualTo(0);
+        assertEquals(2, matcher.isMatch(INPUT2, 1, 1, INPUT2_LENGTH));
+        assertEquals(2, matcher.isMatch(INPUT2, 1, 0, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, 2));
     }
 
     @Test
     public void testNoneMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.noneMatcher();
         assertEquals(0, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.noneMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.noneMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 0, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 8, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 9, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 1, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 3, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 5, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 7, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 8, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 9, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 11, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 12, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 8)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 9)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0));
+        assertEquals(0, matcher.isMatch(INPUT1, 1));
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(0, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(0, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
+        assertEquals(0, matcher.isMatch(INPUT1, 7));
+        assertEquals(0, matcher.isMatch(INPUT1, 8));
+        assertEquals(0, matcher.isMatch(INPUT1, 9));
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
+        assertEquals(0, matcher.isMatch(INPUT1, 11));
+        assertEquals(0, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
     public void testQuoteMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.quoteMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.quoteMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.quoteMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 11, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 12, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
+        assertEquals(1, matcher.isMatch(INPUT1, 11));
+        assertEquals(1, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
     public void testSingleQuoteMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.singleQuoteMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.singleQuoteMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.singleQuoteMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 11, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 12, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
+        assertEquals(1, matcher.isMatch(INPUT1, 11));
+        assertEquals(0, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
     public void testSpaceMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.spaceMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.spaceMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.spaceMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 5, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(1, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
     }
 
     @Test
     public void testSplitMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.splitMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.splitMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.splitMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 3, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 5, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 7, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 8, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 9, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(1, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(1, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
+        assertEquals(1, matcher.isMatch(INPUT1, 7));
+        assertEquals(1, matcher.isMatch(INPUT1, 8));
+        assertEquals(1, matcher.isMatch(INPUT1, 9));
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
     }
 
     private void testStringMatcher_String(final StringMatcher matcher) {
         assertEquals(2, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(2, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0));
+        assertEquals(2, matcher.isMatch(INPUT2, 1));
+        assertEquals(0, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
         //
-        assertThat(StringMatcherFactory.INSTANCE.stringMatcher(""))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.stringMatcher((String) null))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.stringMatcher(""), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.stringMatcher((String) null), StringMatcherFactory.INSTANCE.noneMatcher());
     }
 
     @Test
     public void testStringMatcher_String_fromChars() {
         testStringMatcher_String(StringMatcherFactory.INSTANCE.stringMatcher('b', 'c'));
-        testStringMatcher_String(StringMatcherFactory.INSTANCE.stringMatcher(new char[] {'b', 'c'}));
+        testStringMatcher_String(StringMatcherFactory.INSTANCE.stringMatcher(new char[] { 'b', 'c' }));
     }
 
     @Test
@@ -317,46 +309,46 @@ public class StringMatcherOnCharArrayTest {
         testStringMatcher_String(StringMatcherFactory.INSTANCE.stringMatcher("bc"));
     }
 
-     @Test
+    @Test
     public void testTabMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.tabMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.tabMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.tabMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 3, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(1, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
     }
 
     @Test
     public void testTrimMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.trimMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.trimMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.trimMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9, 0, INPUT1.length)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 3, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 5, 0, INPUT1.length));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 7, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 8, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 9, 0, INPUT1.length));
+        assertEquals(1, matcher.isMatch(INPUT1, 10, 0, INPUT1.length));
         //
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(1, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(1, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
+        assertEquals(1, matcher.isMatch(INPUT1, 7));
+        assertEquals(1, matcher.isMatch(INPUT1, 8));
+        assertEquals(1, matcher.isMatch(INPUT1, 9));
+        assertEquals(1, matcher.isMatch(INPUT1, 10));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharSequenceStringTest.java b/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharSequenceStringTest.java
index 1c71fe1c..cce37553 100644
--- a/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharSequenceStringTest.java
+++ b/src/test/java/org/apache/commons/text/matcher/StringMatcherOnCharSequenceStringTest.java
@@ -16,8 +16,9 @@
  */
 package org.apache.commons.text.matcher;
 
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertSame;
 
 import org.junit.jupiter.api.Test;
 
@@ -33,31 +34,30 @@ public class StringMatcherOnCharSequenceStringTest {
     private static final int INPUT2_LENGTH = INPUT2.length();
 
     private void checkAndMatcher_char(final StringMatcher matcher) {
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(3);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(3, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(3);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(3, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
     }
 
     @Test
     public void testAndMatcher_char() {
-        final StringMatcher matcher1 = StringMatcherFactory.INSTANCE.andMatcher(
-            StringMatcherFactory.INSTANCE.charMatcher('c'), StringMatcherFactory.INSTANCE.stringMatcher("de"));
+        final StringMatcher matcher1 = StringMatcherFactory.INSTANCE.andMatcher(StringMatcherFactory.INSTANCE.charMatcher('c'),
+                StringMatcherFactory.INSTANCE.stringMatcher("de"));
         assertEquals(3, matcher1.size());
         checkAndMatcher_char(matcher1);
         //
-        final StringMatcher matcher2 = StringMatcherFactory.INSTANCE.andMatcher(null,
-            StringMatcherFactory.INSTANCE.charMatcher('c'), null, StringMatcherFactory.INSTANCE.stringMatcher("de"),
-            null);
+        final StringMatcher matcher2 = StringMatcherFactory.INSTANCE.andMatcher(null, StringMatcherFactory.INSTANCE.charMatcher('c'), null,
+                StringMatcherFactory.INSTANCE.stringMatcher("de"), null);
         assertEquals(3, matcher2.size());
         checkAndMatcher_char(matcher2);
     }
@@ -67,19 +67,19 @@ public class StringMatcherOnCharSequenceStringTest {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.charMatcher('c');
         assertEquals(1, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(1, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
     }
 
     @Test
@@ -87,26 +87,23 @@ public class StringMatcherOnCharSequenceStringTest {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.charSetMatcher("ace".toCharArray());
         assertEquals(1, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(1, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(1, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
         //
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher())
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher((char[]) null))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE
-            .charSetMatcher("a".toCharArray()) instanceof AbstractStringMatcher.CharMatcher).isTrue();
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher(), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher((char[]) null), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertInstanceOf(AbstractStringMatcher.CharMatcher.class, StringMatcherFactory.INSTANCE.charSetMatcher("a".toCharArray()));
     }
 
     @Test
@@ -114,54 +111,51 @@ public class StringMatcherOnCharSequenceStringTest {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.charSetMatcher("ace");
         assertEquals(1, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(1, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(1, matcher.isMatch(INPUT2, 0));
+        assertEquals(0, matcher.isMatch(INPUT2, 1));
+        assertEquals(1, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(1, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
         //
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher(""))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher((String) null))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.charSetMatcher("a") instanceof AbstractStringMatcher.CharMatcher)
-            .isTrue();
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher(""), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.charSetMatcher((String) null), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertInstanceOf(AbstractStringMatcher.CharMatcher.class, StringMatcherFactory.INSTANCE.charSetMatcher("a"));
     }
 
     @Test
     public void testCommaMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.commaMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.commaMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.commaMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 0, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length())).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 1, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0));
+        assertEquals(1, matcher.isMatch(INPUT1, 1));
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
     }
 
     @Test
     public void testDoubleQuoteMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.doubleQuoteMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.doubleQuoteMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.doubleQuoteMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length())).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 11, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 12, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 11));
+        assertEquals(1, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
@@ -171,116 +165,116 @@ public class StringMatcherOnCharSequenceStringTest {
         // the concern of StringMatcher, and are not bugs
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.stringMatcher("bc");
         assertEquals(2, matcher.size());
-        assertThat(matcher.isMatch(INPUT2, 1, 1, INPUT2_LENGTH)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, 3)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, 2)).isEqualTo(0);
+        assertEquals(2, matcher.isMatch(INPUT2, 1, 1, INPUT2_LENGTH));
+        assertEquals(2, matcher.isMatch(INPUT2, 1, 0, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 1, 0, 2));
     }
 
     @Test
     public void testNoneMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.noneMatcher();
         assertEquals(0, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.noneMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.noneMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 0, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 8, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 9, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length())).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 1, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 3, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 5, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 7, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 8, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 9, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 11, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 12, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 1)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 8)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 9)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 0));
+        assertEquals(0, matcher.isMatch(INPUT1, 1));
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(0, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(0, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
+        assertEquals(0, matcher.isMatch(INPUT1, 7));
+        assertEquals(0, matcher.isMatch(INPUT1, 8));
+        assertEquals(0, matcher.isMatch(INPUT1, 9));
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
+        assertEquals(0, matcher.isMatch(INPUT1, 11));
+        assertEquals(0, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
     public void testQuoteMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.quoteMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.quoteMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.quoteMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length())).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 11, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 12, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
+        assertEquals(1, matcher.isMatch(INPUT1, 11));
+        assertEquals(1, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
     public void testSingleQuoteMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.singleQuoteMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.singleQuoteMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.singleQuoteMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12, 0, INPUT1.length())).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 11, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 12, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 11)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 12)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
+        assertEquals(1, matcher.isMatch(INPUT1, 11));
+        assertEquals(0, matcher.isMatch(INPUT1, 12));
     }
 
     @Test
     public void testSpaceMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.spaceMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.spaceMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.spaceMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length())).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 5, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(1, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
     }
 
     @Test
     public void testSplitMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.splitMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.splitMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.splitMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length())).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 3, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 5, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 7, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 8, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 9, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 10, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(1, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(1, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
+        assertEquals(1, matcher.isMatch(INPUT1, 7));
+        assertEquals(1, matcher.isMatch(INPUT1, 8));
+        assertEquals(1, matcher.isMatch(INPUT1, 9));
+        assertEquals(0, matcher.isMatch(INPUT1, 10));
     }
 
     @Test
@@ -288,66 +282,64 @@ public class StringMatcherOnCharSequenceStringTest {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.stringMatcher("bc");
         assertEquals(2, matcher.size());
         //
-        assertThat(matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0, 0, INPUT2_LENGTH));
+        assertEquals(2, matcher.isMatch(INPUT2, 1, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 2, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 3, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 4, 0, INPUT2_LENGTH));
+        assertEquals(0, matcher.isMatch(INPUT2, 5, 0, INPUT2_LENGTH));
         //
-        assertThat(matcher.isMatch(INPUT2, 0)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 1)).isEqualTo(2);
-        assertThat(matcher.isMatch(INPUT2, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 3)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT2, 5)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT2, 0));
+        assertEquals(2, matcher.isMatch(INPUT2, 1));
+        assertEquals(0, matcher.isMatch(INPUT2, 2));
+        assertEquals(0, matcher.isMatch(INPUT2, 3));
+        assertEquals(0, matcher.isMatch(INPUT2, 4));
+        assertEquals(0, matcher.isMatch(INPUT2, 5));
         //
-        assertThat(StringMatcherFactory.INSTANCE.stringMatcher(""))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
-        assertThat(StringMatcherFactory.INSTANCE.stringMatcher((String) null))
-            .isSameAs(StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.stringMatcher(""), StringMatcherFactory.INSTANCE.noneMatcher());
+        assertSame(StringMatcherFactory.INSTANCE.stringMatcher((String) null), StringMatcherFactory.INSTANCE.noneMatcher());
     }
 
-     @Test
+    @Test
     public void testTabMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.tabMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.tabMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.tabMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length())).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 3, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(1, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
     }
 
     @Test
     public void testTrimMatcher() {
         final StringMatcher matcher = StringMatcherFactory.INSTANCE.trimMatcher();
         assertEquals(1, matcher.size());
-        assertThat(StringMatcherFactory.INSTANCE.trimMatcher()).isSameAs(matcher);
+        assertSame(StringMatcherFactory.INSTANCE.trimMatcher(), matcher);
         //
-        assertThat(matcher.isMatch(INPUT1, 2, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6, 0, INPUT1.length())).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9, 0, INPUT1.length())).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10, 0, INPUT1.length())).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 2, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 3, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 4, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 5, 0, INPUT1.length()));
+        assertEquals(0, matcher.isMatch(INPUT1, 6, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 7, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 8, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 9, 0, INPUT1.length()));
+        assertEquals(1, matcher.isMatch(INPUT1, 10, 0, INPUT1.length()));
         //
-        assertThat(matcher.isMatch(INPUT1, 2)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 3)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 4)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 5)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 6)).isEqualTo(0);
-        assertThat(matcher.isMatch(INPUT1, 7)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 8)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 9)).isEqualTo(1);
-        assertThat(matcher.isMatch(INPUT1, 10)).isEqualTo(1);
+        assertEquals(0, matcher.isMatch(INPUT1, 2));
+        assertEquals(1, matcher.isMatch(INPUT1, 3));
+        assertEquals(0, matcher.isMatch(INPUT1, 4));
+        assertEquals(1, matcher.isMatch(INPUT1, 5));
+        assertEquals(0, matcher.isMatch(INPUT1, 6));
+        assertEquals(1, matcher.isMatch(INPUT1, 7));
+        assertEquals(1, matcher.isMatch(INPUT1, 8));
+        assertEquals(1, matcher.isMatch(INPUT1, 9));
+        assertEquals(1, matcher.isMatch(INPUT1, 10));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/CosineDistanceTest.java b/src/test/java/org/apache/commons/text/similarity/CosineDistanceTest.java
index 2781e776..b914c4ae 100644
--- a/src/test/java/org/apache/commons/text/similarity/CosineDistanceTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/CosineDistanceTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
@@ -57,13 +57,12 @@ public class CosineDistanceTest {
      */
     @Test
     public void testCosineDistance() {
-        assertThat(roundValue(cosineDistance.apply("the house", "da house"))).isEqualTo(Double.valueOf(0.5d));
-        assertThat(roundValue(cosineDistance.apply("AB", "AB"))).isEqualTo(Double.valueOf(0.0d));
-        assertThat(roundValue(cosineDistance.apply("AB", "BA"))).isEqualTo(Double.valueOf(1.0d));
-        assertThat(roundValue(cosineDistance.apply(
+        assertEquals(Double.valueOf(0.5d), roundValue(cosineDistance.apply("the house", "da house")));
+        assertEquals(Double.valueOf(0.0d), roundValue(cosineDistance.apply("AB", "AB")));
+        assertEquals(Double.valueOf(1.0d), roundValue(cosineDistance.apply("AB", "BA")));
+        assertEquals(Double.valueOf(0.08d), roundValue(cosineDistance.apply(
                 "the boy was from tamana shi, kumamoto ken, and the girl was from rio de janeiro, rio",
-                "the boy was from tamana shi, kumamoto, and the boy was from rio de janeiro, rio de janeiro")))
-                .isEqualTo(Double.valueOf(0.08d));
+                "the boy was from tamana shi, kumamoto, and the boy was from rio de janeiro, rio de janeiro")));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java b/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java
index 8d968e89..b5380a99 100644
--- a/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/CosineSimilarityTest.java
@@ -17,9 +17,8 @@
 
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
-import static org.assertj.core.api.Assertions.within;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -31,15 +30,12 @@ public class CosineSimilarityTest {
     @Test
     public void testCosineSimilarityReturningDoubleWhereByteValueIsZero() {
         final Map<CharSequence, Integer> hashMap = new HashMap<>();
-        assertThat(CosineSimilarity.INSTANCE.cosineSimilarity(hashMap, hashMap)).isEqualTo(0.0, within(0.01));
+        assertEquals(0.0, CosineSimilarity.INSTANCE.cosineSimilarity(hashMap, hashMap), 0.01);
     }
 
     @Test
     public void testCosineSimilarityThrowsIllegalArgumentException() {
-        assertThatIllegalArgumentException().isThrownBy(() -> {
-            final Map<CharSequence, Integer> map = new HashMap<>();
-            CosineSimilarity.INSTANCE.cosineSimilarity(map, null);
-        });
+        assertThrows(IllegalArgumentException.class, () -> CosineSimilarity.INSTANCE.cosineSimilarity(new HashMap<>(), null));
     }
 
     @Test
@@ -48,15 +44,12 @@ public class CosineSimilarityTest {
         final Integer integer = -397;
         hashMap.put("3J/$3.L", integer);
         final Map<CharSequence, Integer> hashMapTwo = new HashMap<>();
-
-        assertThat(CosineSimilarity.INSTANCE.cosineSimilarity(hashMap, hashMapTwo)).isEqualTo(0.0, within(0.01));
+        assertEquals(0.0, CosineSimilarity.INSTANCE.cosineSimilarity(hashMap, hashMapTwo), 0.01);
     }
 
     @Test
     public void testCosineSimilarityWithNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> {
-            CosineSimilarity.INSTANCE.cosineSimilarity(null, null);
-        });
+        assertThrows(IllegalArgumentException.class, () -> CosineSimilarity.INSTANCE.cosineSimilarity(null, null));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/FuzzyScoreTest.java b/src/test/java/org/apache/commons/text/similarity/FuzzyScoreTest.java
index 3a5ac0d2..b1acb4de 100644
--- a/src/test/java/org/apache/commons/text/similarity/FuzzyScoreTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/FuzzyScoreTest.java
@@ -16,8 +16,9 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.util.Locale;
 
@@ -32,28 +33,28 @@ public class FuzzyScoreTest {
 
     @Test
     public void testGetFuzzyScore() {
-        assertThat(ENGLISH_SCORE.fuzzyScore("", "")).isEqualTo(0);
-        assertThat(ENGLISH_SCORE.fuzzyScore("Workshop", "b")).isEqualTo(0);
-        assertThat(ENGLISH_SCORE.fuzzyScore("Room", "o")).isEqualTo(1);
-        assertThat(ENGLISH_SCORE.fuzzyScore("Workshop", "w")).isEqualTo(1);
-        assertThat(ENGLISH_SCORE.fuzzyScore("Workshop", "ws")).isEqualTo(2);
-        assertThat(ENGLISH_SCORE.fuzzyScore("Workshop", "wo")).isEqualTo(4);
-        assertThat(ENGLISH_SCORE.fuzzyScore("Apache Software Foundation", "asf")).isEqualTo(3);
+        assertEquals(0, ENGLISH_SCORE.fuzzyScore("", ""));
+        assertEquals(0, ENGLISH_SCORE.fuzzyScore("Workshop", "b"));
+        assertEquals(1, ENGLISH_SCORE.fuzzyScore("Room", "o"));
+        assertEquals(1, ENGLISH_SCORE.fuzzyScore("Workshop", "w"));
+        assertEquals(2, ENGLISH_SCORE.fuzzyScore("Workshop", "ws"));
+        assertEquals(4, ENGLISH_SCORE.fuzzyScore("Workshop", "wo"));
+        assertEquals(3, ENGLISH_SCORE.fuzzyScore("Apache Software Foundation", "asf"));
     }
 
     @Test
     public void testGetFuzzyScore_NullNullLocale() {
-        assertThatIllegalArgumentException().isThrownBy(() -> ENGLISH_SCORE.fuzzyScore(null, null));
+        assertThrows(IllegalArgumentException.class, () -> ENGLISH_SCORE.fuzzyScore(null, null));
     }
 
     @Test
     public void testGetFuzzyScore_NullStringLocale() {
-        assertThatIllegalArgumentException().isThrownBy(() -> ENGLISH_SCORE.fuzzyScore(null, "not null"));
+        assertThrows(IllegalArgumentException.class, () -> ENGLISH_SCORE.fuzzyScore(null, "not null"));
     }
 
     @Test
     public void testGetFuzzyScore_StringNullLocale() {
-        assertThatIllegalArgumentException().isThrownBy(() -> ENGLISH_SCORE.fuzzyScore("not null", null));
+        assertThrows(IllegalArgumentException.class, () -> ENGLISH_SCORE.fuzzyScore("not null", null));
     }
 
     @Test
@@ -61,13 +62,12 @@ public class FuzzyScoreTest {
         final Locale locale = Locale.CANADA_FRENCH;
         final FuzzyScore fuzzyScore = new FuzzyScore(locale);
         final Locale localeTwo = fuzzyScore.getLocale();
-
-        assertThat(localeTwo).isSameAs(locale);
+        assertSame(localeTwo, locale);
     }
 
     @Test
     public void testMissingLocale() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new FuzzyScore((Locale) null));
+        assertThrows(IllegalArgumentException.class, () -> new FuzzyScore((Locale) null));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/HammingDistanceTest.java b/src/test/java/org/apache/commons/text/similarity/HammingDistanceTest.java
index 1fa1f0b3..8e5cebb8 100644
--- a/src/test/java/org/apache/commons/text/similarity/HammingDistanceTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/HammingDistanceTest.java
@@ -49,6 +49,16 @@ public class HammingDistanceTest {
         assertEquals(2, distance.apply(SimilarityInputTest.build(cls, "ATCG"), SimilarityInputTest.build(cls, "ACCC")));
     }
 
+    @Test
+    public void testHammingDistance_nullLeftValue() {
+        assertThrows(IllegalArgumentException.class, () -> distance.apply(null, ""));
+    }
+
+    @Test
+    public void testHammingDistance_nullRightValue() {
+        assertThrows(IllegalArgumentException.class, () -> distance.apply("", null));
+    }
+
     @Test
     public void testHammingDistanceCharSequence() {
         assertEquals(0, distance.apply("", ""));
@@ -61,14 +71,4 @@ public class HammingDistanceTest {
         assertEquals(2, distance.apply("ATCG", "ACCC"));
     }
 
-    @Test
-    public void testHammingDistance_nullLeftValue() {
-        assertThrows(IllegalArgumentException.class, () -> distance.apply(null, ""));
-    }
-
-    @Test
-    public void testHammingDistance_nullRightValue() {
-        assertThrows(IllegalArgumentException.class, () -> distance.apply("", null));
-    }
-
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/IntersectionSimilarityTest.java b/src/test/java/org/apache/commons/text/similarity/IntersectionSimilarityTest.java
index 76b1d92c..1236fec7 100644
--- a/src/test/java/org/apache/commons/text/similarity/IntersectionSimilarityTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/IntersectionSimilarityTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -36,7 +36,7 @@ import org.junit.jupiter.api.Test;
  */
 public class IntersectionSimilarityTest {
     private static <T> void assertIntersection(final IntersectionSimilarity<T> similarity, final CharSequence cs1, final CharSequence cs2, final int sizeA,
-        final int sizeB, final int intersection) {
+            final int sizeB, final int intersection) {
         final IntersectionResult result = similarity.apply(cs1, cs2);
         assertEquals(sizeA, result.getSizeA(), "Size A error");
         assertEquals(sizeB, result.getSizeB(), "Size B error");
@@ -44,8 +44,7 @@ public class IntersectionSimilarityTest {
     }
 
     /**
-     * Convert the {@link CharSequence} to a {@link List} of bigrams (pairs of characters). These are represented using 2
-     * 16-bit chars packed into a 32-bit int.
+     * Convert the {@link CharSequence} to a {@link List} of bigrams (pairs of characters). These are represented using 2 16-bit chars packed into a 32-bit int.
      *
      * @param sequence the sequence
      * @return the list
@@ -65,8 +64,7 @@ public class IntersectionSimilarityTest {
     }
 
     /**
-     * Convert the {@link CharSequence} to a {@link Set} of bigrams (pairs of characters). These are represented using 2
-     * 16-bit chars packed into a 32-bit int.
+     * Convert the {@link CharSequence} to a {@link Set} of bigrams (pairs of characters). These are represented using 2 16-bit chars packed into a 32-bit int.
      *
      * @param sequence the sequence
      * @return the set
@@ -123,25 +121,24 @@ public class IntersectionSimilarityTest {
 
     @Test
     public void testApplyNullNull() {
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> new IntersectionSimilarity<>(cs -> new HashSet<>(Collections.singletonList(cs))).apply(null, null));
+        assertThrows(IllegalArgumentException.class, () -> new IntersectionSimilarity<>(cs -> new HashSet<>(Collections.singletonList(cs))).apply(null, null));
     }
 
     @Test
     public void testApplyNullString() {
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> new IntersectionSimilarity<>(cs -> new HashSet<>(Collections.singletonList(cs))).apply(null, "right"));
+        assertThrows(IllegalArgumentException.class,
+                () -> new IntersectionSimilarity<>(cs -> new HashSet<>(Collections.singletonList(cs))).apply(null, "right"));
     }
 
     @Test
     public void testApplyStringNull() {
-        assertThatIllegalArgumentException()
-            .isThrownBy(() -> new IntersectionSimilarity<>(cs -> new HashSet<>(Collections.singletonList(cs))).apply("left", null));
+        assertThrows(IllegalArgumentException.class,
+                () -> new IntersectionSimilarity<>(cs -> new HashSet<>(Collections.singletonList(cs))).apply("left", null));
     }
 
     @Test
     public void testConstructorWithNullConverterThrows() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new IntersectionSimilarity<>(null));
+        assertThrows(IllegalArgumentException.class, () -> new IntersectionSimilarity<>(null));
     }
 
     @Test
diff --git a/src/test/java/org/apache/commons/text/similarity/JaccardDistanceTest.java b/src/test/java/org/apache/commons/text/similarity/JaccardDistanceTest.java
index d67e8de5..4339fdf3 100644
--- a/src/test/java/org/apache/commons/text/similarity/JaccardDistanceTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/JaccardDistanceTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -77,16 +77,16 @@ public class JaccardDistanceTest {
 
     @Test
     public void testGettingJaccardDistanceNullNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> classBeingTested.apply((String) null, null));
+        assertThrows(IllegalArgumentException.class, () -> classBeingTested.apply((String) null, null));
     }
 
     @Test
     public void testGettingJaccardDistanceNullString() {
-        assertThatIllegalArgumentException().isThrownBy(() -> classBeingTested.apply(null, "right"));
+        assertThrows(IllegalArgumentException.class, () -> classBeingTested.apply(null, "right"));
     }
 
     @Test
     public void testGettingJaccardDistanceStringNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> classBeingTested.apply(" ", null));
+        assertThrows(IllegalArgumentException.class, () -> classBeingTested.apply(" ", null));
     }
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/JaccardSimilarityTest.java b/src/test/java/org/apache/commons/text/similarity/JaccardSimilarityTest.java
index b3c96532..08c9188e 100644
--- a/src/test/java/org/apache/commons/text/similarity/JaccardSimilarityTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/JaccardSimilarityTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -77,16 +77,16 @@ public class JaccardSimilarityTest {
 
     @Test
     public void testGettingJaccardSimilarityNullNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> classBeingTested.apply((String) null, null));
+        assertThrows(IllegalArgumentException.class, () -> classBeingTested.apply((String) null, null));
     }
 
     @Test
     public void testGettingJaccardSimilarityNullString() {
-        assertThatIllegalArgumentException().isThrownBy(() -> classBeingTested.apply(null, "right"));
+        assertThrows(IllegalArgumentException.class, () -> classBeingTested.apply(null, "right"));
     }
 
     @Test
     public void testGettingJaccardSimilarityStringNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> classBeingTested.apply(" ", null));
+        assertThrows(IllegalArgumentException.class, () -> classBeingTested.apply(" ", null));
     }
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/LevenshteinDistanceTest.java b/src/test/java/org/apache/commons/text/similarity/LevenshteinDistanceTest.java
index 51665928..94840e60 100644
--- a/src/test/java/org/apache/commons/text/similarity/LevenshteinDistanceTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/LevenshteinDistanceTest.java
@@ -32,13 +32,13 @@ public class LevenshteinDistanceTest {
     private static final LevenshteinDistance UNLIMITED_DISTANCE = LevenshteinDistance.getDefaultInstance();
 
     @Test
-    public void testApplyThrowsIllegalArgumentExceptionString() {
-        assertThrows(IllegalArgumentException.class, () -> new LevenshteinDistance(0).apply((String) null, (String) null));
+    public void testApplyThrowsIllegalArgumentExceptionSimilarityInput() {
+        assertThrows(IllegalArgumentException.class, () -> new LevenshteinDistance(0).apply((SimilarityInput<Object>) null, (SimilarityInput<Object>) null));
     }
 
     @Test
-    public void testApplyThrowsIllegalArgumentExceptionSimilarityInput() {
-        assertThrows(IllegalArgumentException.class, () -> new LevenshteinDistance(0).apply((SimilarityInput<Object>) null, (SimilarityInput<Object>) null));
+    public void testApplyThrowsIllegalArgumentExceptionString() {
+        assertThrows(IllegalArgumentException.class, () -> new LevenshteinDistance(0).apply((String) null, (String) null));
     }
 
     @Test
diff --git a/src/test/java/org/apache/commons/text/similarity/LevenshteinResultsTest.java b/src/test/java/org/apache/commons/text/similarity/LevenshteinResultsTest.java
index 68046561..e9a58e10 100644
--- a/src/test/java/org/apache/commons/text/similarity/LevenshteinResultsTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/LevenshteinResultsTest.java
@@ -16,7 +16,8 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import org.junit.jupiter.api.Test;
 
@@ -27,28 +28,23 @@ public class LevenshteinResultsTest {
         final Integer integer = 1662;
         final LevenshteinResults levenshteinResults = new LevenshteinResults(integer, integer, integer, integer);
         final LevenshteinResults levenshteinResultsTwo = new LevenshteinResults(integer, integer, integer, null);
-
-        assertThat(levenshteinResults.equals(levenshteinResultsTwo)).isFalse();
+        assertFalse(levenshteinResults.equals(levenshteinResultsTwo));
     }
 
     @Test
     public void testEqualsReturningFalse() {
         final Integer integerOne = 1662;
         final Integer integerTwo = 1164;
-        final LevenshteinResults levenshteinResults =
-                new LevenshteinResults(integerOne, integerOne, integerOne, integerOne);
-        final LevenshteinResults levenshteinResultsTwo =
-                new LevenshteinResults(integerOne, integerOne, integerTwo, integerTwo);
-
-        assertThat(levenshteinResults.equals(levenshteinResultsTwo)).isFalse();
+        final LevenshteinResults levenshteinResults = new LevenshteinResults(integerOne, integerOne, integerOne, integerOne);
+        final LevenshteinResults levenshteinResultsTwo = new LevenshteinResults(integerOne, integerOne, integerTwo, integerTwo);
+        assertFalse(levenshteinResults.equals(levenshteinResultsTwo));
     }
 
     @Test
     public void testEqualsSameObject() {
         final Integer integer = 1662;
         final LevenshteinResults levenshteinResults = new LevenshteinResults(integer, integer, integer, null);
-
-        assertThat(levenshteinResults.equals(levenshteinResults)).isTrue();
+        assertTrue(levenshteinResults.equals(levenshteinResults));
     }
 
     @Test
@@ -56,16 +52,14 @@ public class LevenshteinResultsTest {
         final Integer integer = 1;
         final LevenshteinResults levenshteinResults = new LevenshteinResults(null, integer, integer, null);
         final LevenshteinResults levenshteinResultsTwo = new LevenshteinResults(null, null, null, null);
-
-        assertThat(levenshteinResults.equals(levenshteinResultsTwo)).isFalse();
+        assertFalse(levenshteinResults.equals(levenshteinResultsTwo));
     }
 
     @Test
     public void testEqualsWithNull() {
         final Integer integer = -647;
         final LevenshteinResults levenshteinResults = new LevenshteinResults(integer, null, null, integer);
-
-        assertThat(levenshteinResults.equals(null)).isFalse();
+        assertFalse(levenshteinResults.equals(null));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistanceTest.java b/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistanceTest.java
index e0ccac52..30dddb4c 100644
--- a/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistanceTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistanceTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -36,34 +36,34 @@ public class LongestCommonSubsequenceDistanceTest {
 
     @Test
     public void testGettingLongestCommonSubsequenceDistance() {
-        assertThat(subject.apply("", "")).isEqualTo(0);
-        assertThat(subject.apply("left", "")).isEqualTo(4);
-        assertThat(subject.apply("", "right")).isEqualTo(5);
-        assertThat(subject.apply("frog", "fog")).isEqualTo(1);
-        assertThat(subject.apply("fly", "ant")).isEqualTo(6);
-        assertThat(subject.apply("elephant", "hippo")).isEqualTo(11);
-        assertThat(subject.apply("ABC Corporation", "ABC Corp")).isEqualTo(7);
-        assertThat(subject.apply("D N H Enterprises Inc", "D & H Enterprises, Inc.")).isEqualTo(4);
-        assertThat(subject.apply("My Gym Children's Fitness Center", "My Gym. Childrens Fitness")).isEqualTo(9);
-        assertThat(subject.apply("PENNSYLVANIA", "PENNCISYLVNIA")).isEqualTo(3);
-        assertThat(subject.apply("left", "right")).isEqualTo(7);
-        assertThat(subject.apply("leettteft", "ritttght")).isEqualTo(9);
-        assertThat(subject.apply("the same string", "the same string")).isEqualTo(0);
+        assertEquals(0, subject.apply("", ""));
+        assertEquals(4, subject.apply("left", ""));
+        assertEquals(5, subject.apply("", "right"));
+        assertEquals(1, subject.apply("frog", "fog"));
+        assertEquals(6, subject.apply("fly", "ant"));
+        assertEquals(11, subject.apply("elephant", "hippo"));
+        assertEquals(7, subject.apply("ABC Corporation", "ABC Corp"));
+        assertEquals(4, subject.apply("D N H Enterprises Inc", "D & H Enterprises, Inc."));
+        assertEquals(9, subject.apply("My Gym Children's Fitness Center", "My Gym. Childrens Fitness"));
+        assertEquals(3, subject.apply("PENNSYLVANIA", "PENNCISYLVNIA"));
+        assertEquals(7, subject.apply("left", "right"));
+        assertEquals(9, subject.apply("leettteft", "ritttght"));
+        assertEquals(0, subject.apply("the same string", "the same string"));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceDistanceNullNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.apply(null, null));
+        assertThrows(IllegalArgumentException.class, () -> subject.apply(null, null));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceDistanceNullString() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.apply(null, "right"));
+        assertThrows(IllegalArgumentException.class, () -> subject.apply(null, "right"));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceDistanceStringNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.apply(" ", null));
+        assertThrows(IllegalArgumentException.class, () -> subject.apply(" ", null));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceTest.java b/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceTest.java
index 8115240d..ea01b5b8 100644
--- a/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/LongestCommonSubsequenceTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
@@ -37,104 +37,100 @@ public class LongestCommonSubsequenceTest {
     @Test
     @SuppressWarnings("deprecation")
     public void testGettingLogestCommonSubsequenceNullNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.logestCommonSubsequence(null, null));
+        assertThrows(IllegalArgumentException.class, () -> subject.logestCommonSubsequence(null, null));
     }
 
     @Test
     @SuppressWarnings("deprecation")
     public void testGettingLogestCommonSubsequenceNullString() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.logestCommonSubsequence(null, "right"));
+        assertThrows(IllegalArgumentException.class, () -> subject.logestCommonSubsequence(null, "right"));
     }
 
     @Test
     @SuppressWarnings("deprecation")
     public void testGettingLogestCommonSubsequenceStringNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.logestCommonSubsequence(" ", null));
+        assertThrows(IllegalArgumentException.class, () -> subject.logestCommonSubsequence(" ", null));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceApplyNullNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.apply(null, null));
+        assertThrows(IllegalArgumentException.class, () -> subject.apply(null, null));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceApplyNullString() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.apply(null, "right"));
+        assertThrows(IllegalArgumentException.class, () -> subject.apply(null, "right"));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceApplyStringNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.apply(" ", null));
+        assertThrows(IllegalArgumentException.class, () -> subject.apply(" ", null));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceNullNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.longestCommonSubsequence(null, null));
+        assertThrows(IllegalArgumentException.class, () -> subject.longestCommonSubsequence(null, null));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceNullString() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.longestCommonSubsequence(null, "right"));
+        assertThrows(IllegalArgumentException.class, () -> subject.longestCommonSubsequence(null, "right"));
     }
 
     @Test
     public void testGettingLongestCommonSubsequenceStringNull() {
-        assertThatIllegalArgumentException().isThrownBy(() -> subject.longestCommonSubsequence(" ", null));
+        assertThrows(IllegalArgumentException.class, () -> subject.longestCommonSubsequence(" ", null));
     }
 
     @Test
     @Deprecated
     public void testLogestCommonSubsequence() {
-        assertThat(subject.logestCommonSubsequence("", "")).isEqualTo("");
-        assertThat(subject.logestCommonSubsequence("left", "")).isEqualTo("");
-        assertThat(subject.logestCommonSubsequence("", "right")).isEqualTo("");
-        assertThat(subject.logestCommonSubsequence("frog", "fog")).isEqualTo("fog");
-        assertThat(subject.logestCommonSubsequence("fly", "ant")).isEqualTo("");
-        assertThat(subject.logestCommonSubsequence("elephant", "hippo")).isEqualTo("h");
-        assertThat(subject.logestCommonSubsequence("ABC Corporation", "ABC Corp")).isEqualTo("ABC Corp");
-        assertThat(subject.logestCommonSubsequence("D N H Enterprises Inc", "D & H Enterprises, Inc."))
-            .isEqualTo("D  H Enterprises Inc");
-        assertThat(subject.logestCommonSubsequence("My Gym Children's Fitness Center", "My Gym. Childrens Fitness"))
-            .isEqualTo("My Gym Childrens Fitness");
-        assertThat(subject.logestCommonSubsequence("PENNSYLVANIA", "PENNCISYLVNIA")).isEqualTo("PENNSYLVNIA");
-        assertThat(subject.logestCommonSubsequence("left", "right")).isEqualTo("t");
-        assertThat(subject.logestCommonSubsequence("leettteft", "ritttght")).isEqualTo("tttt");
-        assertThat(subject.logestCommonSubsequence("the same string", "the same string")).isEqualTo("the same string");
+        assertEquals("", subject.logestCommonSubsequence("", ""));
+        assertEquals("", subject.logestCommonSubsequence("left", ""));
+        assertEquals("", subject.logestCommonSubsequence("", "right"));
+        assertEquals("fog", subject.logestCommonSubsequence("frog", "fog"));
+        assertEquals("", subject.logestCommonSubsequence("fly", "ant"));
+        assertEquals("h", subject.logestCommonSubsequence("elephant", "hippo"));
+        assertEquals("ABC Corp", subject.logestCommonSubsequence("ABC Corporation", "ABC Corp"));
+        assertEquals("D  H Enterprises Inc", subject.logestCommonSubsequence("D N H Enterprises Inc", "D & H Enterprises, Inc."));
+        assertEquals("My Gym Childrens Fitness", subject.logestCommonSubsequence("My Gym Children's Fitness Center", "My Gym. Childrens Fitness"));
+        assertEquals("PENNSYLVNIA", subject.logestCommonSubsequence("PENNSYLVANIA", "PENNCISYLVNIA"));
+        assertEquals("t", subject.logestCommonSubsequence("left", "right"));
+        assertEquals("tttt", subject.logestCommonSubsequence("leettteft", "ritttght"));
+        assertEquals("the same string", subject.logestCommonSubsequence("the same string", "the same string"));
     }
 
     @Test
     public void testLongestCommonSubsequence() {
-        assertThat(subject.longestCommonSubsequence("", "")).isEqualTo("");
-        assertThat(subject.longestCommonSubsequence("left", "")).isEqualTo("");
-        assertThat(subject.longestCommonSubsequence("", "right")).isEqualTo("");
-        assertThat(subject.longestCommonSubsequence("frog", "fog")).isEqualTo("fog");
-        assertThat(subject.longestCommonSubsequence("fly", "ant")).isEqualTo("");
-        assertThat(subject.longestCommonSubsequence("elephant", "hippo")).isEqualTo("h");
-        assertThat(subject.longestCommonSubsequence("ABC Corporation", "ABC Corp")).isEqualTo("ABC Corp");
-        assertThat(subject.longestCommonSubsequence("D N H Enterprises Inc", "D & H Enterprises, Inc."))
-            .isEqualTo("D  H Enterprises Inc");
-        assertThat(subject.longestCommonSubsequence("My Gym Children's Fitness Center", "My Gym. Childrens Fitness"))
-            .isEqualTo("My Gym Childrens Fitness");
-        assertThat(subject.longestCommonSubsequence("PENNSYLVANIA", "PENNCISYLVNIA")).isEqualTo("PENNSYLVNIA");
-        assertThat(subject.longestCommonSubsequence("left", "right")).isEqualTo("t");
-        assertThat(subject.longestCommonSubsequence("leettteft", "ritttght")).isEqualTo("tttt");
-        assertThat(subject.longestCommonSubsequence("the same string", "the same string")).isEqualTo("the same string");
+        assertEquals("", subject.longestCommonSubsequence("", ""));
+        assertEquals("", subject.longestCommonSubsequence("left", ""));
+        assertEquals("", subject.longestCommonSubsequence("", "right"));
+        assertEquals("fog", subject.longestCommonSubsequence("frog", "fog"));
+        assertEquals("", subject.longestCommonSubsequence("fly", "ant"));
+        assertEquals("h", subject.longestCommonSubsequence("elephant", "hippo"));
+        assertEquals("ABC Corp", subject.longestCommonSubsequence("ABC Corporation", "ABC Corp"));
+        assertEquals("D  H Enterprises Inc", subject.longestCommonSubsequence("D N H Enterprises Inc", "D & H Enterprises, Inc."));
+        assertEquals("My Gym Childrens Fitness", subject.longestCommonSubsequence("My Gym Children's Fitness Center", "My Gym. Childrens Fitness"));
+        assertEquals("PENNSYLVNIA", subject.longestCommonSubsequence("PENNSYLVANIA", "PENNCISYLVNIA"));
+        assertEquals("t", subject.longestCommonSubsequence("left", "right"));
+        assertEquals("tttt", subject.longestCommonSubsequence("leettteft", "ritttght"));
+        assertEquals("the same string", subject.longestCommonSubsequence("the same string", "the same string"));
     }
 
     @Test
     public void testLongestCommonSubsequenceApply() {
-        assertThat(subject.apply("", "")).isEqualTo(0);
-        assertThat(subject.apply("left", "")).isEqualTo(0);
-        assertThat(subject.apply("", "right")).isEqualTo(0);
-        assertThat(subject.apply("frog", "fog")).isEqualTo(3);
-        assertThat(subject.apply("fly", "ant")).isEqualTo(0);
-        assertThat(subject.apply("elephant", "hippo")).isEqualTo(1);
-        assertThat(subject.apply("ABC Corporation", "ABC Corp")).isEqualTo(8);
-        assertThat(subject.apply("D N H Enterprises Inc", "D & H Enterprises, Inc.")).isEqualTo(20);
-        assertThat(subject.apply("My Gym Children's Fitness Center", "My Gym. Childrens Fitness")).isEqualTo(24);
-        assertThat(subject.apply("PENNSYLVANIA", "PENNCISYLVNIA")).isEqualTo(11);
-        assertThat(subject.apply("left", "right")).isEqualTo(1);
-        assertThat(subject.apply("leettteft", "ritttght")).isEqualTo(4);
-        assertThat(subject.apply("the same string", "the same string")).isEqualTo(15);
+        assertEquals(0, subject.apply("", ""));
+        assertEquals(0, subject.apply("left", ""));
+        assertEquals(0, subject.apply("", "right"));
+        assertEquals(3, subject.apply("frog", "fog"));
+        assertEquals(0, subject.apply("fly", "ant"));
+        assertEquals(1, subject.apply("elephant", "hippo"));
+        assertEquals(8, subject.apply("ABC Corporation", "ABC Corp"));
+        assertEquals(20, subject.apply("D N H Enterprises Inc", "D & H Enterprises, Inc."));
+        assertEquals(24, subject.apply("My Gym Children's Fitness Center", "My Gym. Childrens Fitness"));
+        assertEquals(11, subject.apply("PENNSYLVANIA", "PENNCISYLVNIA"));
+        assertEquals(1, subject.apply("left", "right"));
+        assertEquals(4, subject.apply("leettteft", "ritttght"));
+        assertEquals(15, subject.apply("the same string", "the same string"));
     }
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/ParameterizedEditDistanceFromTest.java b/src/test/java/org/apache/commons/text/similarity/ParameterizedEditDistanceFromTest.java
index 1373d1a6..420200e5 100644
--- a/src/test/java/org/apache/commons/text/similarity/ParameterizedEditDistanceFromTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/ParameterizedEditDistanceFromTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.stream.Stream;
 
@@ -54,10 +54,9 @@ public class ParameterizedEditDistanceFromTest<R> {
 
     @ParameterizedTest
     @MethodSource("parameters")
-    public void test(final EditDistance<R> editDistance, final CharSequence left, final CharSequence right,
-            final R distance) {
+    public void test(final EditDistance<R> editDistance, final CharSequence left, final CharSequence right, final R distance) {
         final EditDistanceFrom<R> editDistanceFrom = new EditDistanceFrom<>(editDistance, left);
-        assertThat(editDistanceFrom.apply(right)).isEqualTo(distance);
+        assertEquals(distance, editDistanceFrom.apply(right));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/ParameterizedLevenshteinDistanceTest.java b/src/test/java/org/apache/commons/text/similarity/ParameterizedLevenshteinDistanceTest.java
index 2c272e73..fb75cd87 100644
--- a/src/test/java/org/apache/commons/text/similarity/ParameterizedLevenshteinDistanceTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/ParameterizedLevenshteinDistanceTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.stream.Stream;
 
@@ -30,6 +30,7 @@ import org.junit.jupiter.params.provider.MethodSource;
 public class ParameterizedLevenshteinDistanceTest {
 
     public static Stream<Arguments> parameters() {
+        // @formatter:off
         return Stream.of(
             /* empty strings */
             Arguments.of(0, "", "", 0),
@@ -91,14 +92,13 @@ public class ParameterizedLevenshteinDistanceTest {
             Arguments.of(Integer.MAX_VALUE, "hippo", "zzzzzzzz", 8),
             Arguments.of(Integer.MAX_VALUE, "zzzzzzzz", "hippo", 8),
             Arguments.of(Integer.MAX_VALUE, "hello", "hallo", 1));
+        // @formatter:on
     }
 
     @ParameterizedTest
     @MethodSource("parameters")
-    public void test(final Integer threshold, final CharSequence left, final CharSequence right,
-            final Integer distance) {
-        final LevenshteinDistance metric = new LevenshteinDistance(threshold);
-        assertThat(metric.apply(left, right)).isEqualTo(distance);
+    public void test(final Integer threshold, final CharSequence left, final CharSequence right, final Integer distance) {
+        assertEquals(distance, new LevenshteinDistance(threshold).apply(left, right));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/ParameterizedSimilarityScoreFromTest.java b/src/test/java/org/apache/commons/text/similarity/ParameterizedSimilarityScoreFromTest.java
index 40fae22c..6520daf6 100644
--- a/src/test/java/org/apache/commons/text/similarity/ParameterizedSimilarityScoreFromTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/ParameterizedSimilarityScoreFromTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.stream.Stream;
 
@@ -32,25 +32,17 @@ import org.junit.jupiter.params.provider.MethodSource;
 public class ParameterizedSimilarityScoreFromTest<R> {
 
     public static Stream<Arguments> parameters() {
-        return Stream.of(
-                Arguments.of(LevenshteinDistance.getDefaultInstance(), "elephant", "hippo", 7),
+        return Stream.of(Arguments.of(LevenshteinDistance.getDefaultInstance(), "elephant", "hippo", 7),
                 Arguments.of(LevenshteinDistance.getDefaultInstance(), "hippo", "elephant", 7),
                 Arguments.of(LevenshteinDistance.getDefaultInstance(), "hippo", "zzzzzzzz", 8),
-
-                Arguments.of(
-                        (SimilarityScore<Boolean>) (left, right) -> left == right
-                                || left != null && left.equals(right),
-                        "Bob's your uncle.",
-                        "Every good boy does fine.",
-                        false
-                ));
+                Arguments.of((SimilarityScore<Boolean>) (left, right) -> left == right || left != null && left.equals(right), "Bob's your uncle.",
+                        "Every good boy does fine.", false));
     }
 
     @ParameterizedTest
     @MethodSource("parameters")
-    public void test(final SimilarityScore<R> similarityScore, final CharSequence left, final CharSequence right,
-            final R distance) {
+    public void test(final SimilarityScore<R> similarityScore, final CharSequence left, final CharSequence right, final R distance) {
         final SimilarityScoreFrom<R> similarityScoreFrom = new SimilarityScoreFrom<>(similarityScore, left);
-        assertThat(similarityScoreFrom.apply(right)).isEqualTo(distance);
+        assertEquals(distance, similarityScoreFrom.apply(right));
     }
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/SimilarityScoreFromTest.java b/src/test/java/org/apache/commons/text/similarity/SimilarityScoreFromTest.java
index 24eac1d0..5dffc285 100644
--- a/src/test/java/org/apache/commons/text/similarity/SimilarityScoreFromTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/SimilarityScoreFromTest.java
@@ -17,8 +17,8 @@
 
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
 
@@ -27,15 +27,13 @@ public class SimilarityScoreFromTest {
     @Test
     public void testApply() {
         final LongestCommonSubsequence longestCommonSubsequence = new LongestCommonSubsequence();
-        final SimilarityScoreFrom<Integer> similarityScoreFrom =
-                new SimilarityScoreFrom<>(longestCommonSubsequence, "asdf");
-
-        assertThat(similarityScoreFrom.apply("s")).isEqualTo(1);
+        final SimilarityScoreFrom<Integer> similarityScoreFrom = new SimilarityScoreFrom<>(longestCommonSubsequence, "asdf");
+        assertEquals(1, similarityScoreFrom.apply("s"));
     }
 
     @Test
     public void testFailsToCreateSimilarityScoreFromThrowsIllegalArgumentException() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new SimilarityScoreFrom<>(null, ""));
+        assertThrows(IllegalArgumentException.class, () -> new SimilarityScoreFrom<>(null, ""));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/similarity/StringMetricFromTest.java b/src/test/java/org/apache/commons/text/similarity/StringMetricFromTest.java
index cffa4f5d..3ee73290 100644
--- a/src/test/java/org/apache/commons/text/similarity/StringMetricFromTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/StringMetricFromTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.similarity;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
 
@@ -34,33 +34,32 @@ public class StringMetricFromTest {
         final Integer distance = 4;
         final EditDistanceFrom<Integer> metricFrom = new EditDistanceFrom<>(metric, left);
 
-        assertThat(metricFrom.apply(right)).isEqualTo(distance);
-        assertThat(metricFrom.apply(right)).isEqualTo(metric.apply(left, right));
+        assertEquals(distance, metricFrom.apply(right));
+        assertEquals(metric.apply(left, right), metricFrom.apply(right));
     }
 
     @Test
     public void testJavadocExample() {
         final EditDistance<Integer> metric = LevenshteinDistance.getDefaultInstance();
         final String target = "Apache";
-        final EditDistanceFrom<Integer> metricFrom =
-            new EditDistanceFrom<>(metric, target);
+        final EditDistanceFrom<Integer> metricFrom = new EditDistanceFrom<>(metric, target);
         String mostSimilar = null;
         Integer shortestDistance = null;
 
-        for (final String test : new String[] {"Appaloosa", "a patchy", "apple" }) {
+        for (final String test : new String[] { "Appaloosa", "a patchy", "apple" }) {
             final Integer distance = metricFrom.apply(test);
             if (shortestDistance == null || distance < shortestDistance) {
                 shortestDistance = distance;
                 mostSimilar = test;
             }
         }
-        assertThat(mostSimilar).isEqualTo("a patchy");
-        assertThat(shortestDistance).isEqualTo(4);
+        assertEquals("a patchy", mostSimilar);
+        assertEquals(4, shortestDistance);
     }
 
     @Test
     public void testMissingMetric() {
-        assertThatIllegalArgumentException().isThrownBy(() -> new EditDistanceFrom<Number>(null, "no go"));
+        assertThrows(IllegalArgumentException.class, () -> new EditDistanceFrom<Number>(null, "no go"));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/translate/AggregateTranslatorTest.java b/src/test/java/org/apache/commons/text/translate/AggregateTranslatorTest.java
index a3bdc9d8..99fa2efd 100644
--- a/src/test/java/org/apache/commons/text/translate/AggregateTranslatorTest.java
+++ b/src/test/java/org/apache/commons/text/translate/AggregateTranslatorTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.io.IOException;
 import java.io.StringWriter;
@@ -41,26 +41,26 @@ public class AggregateTranslatorTest {
         final AggregateTranslator subject = new AggregateTranslator(translator1, translator2);
         final StringWriter out1 = new StringWriter();
         final int result1 = subject.translate(new StringBuffer("one"), 0, out1);
-        assertThat(result1).as("Incorrect code point consumption").isEqualTo(3);
-        assertThat(out1.toString()).as("Incorrect value").isEqualTo("two");
+        assertEquals(3, result1, "Incorrect code point consumption");
+        assertEquals("two", out1.toString());
         final StringWriter out2 = new StringWriter();
         final int result2 = subject.translate(new StringBuffer("three"), 0, out2);
-        assertThat(result2).as("Incorrect code point consumption").isEqualTo(5);
-        assertThat(out2.toString()).as("Incorrect value").isEqualTo("four");
+        assertEquals(5, result2, "Incorrect code point consumption");
+        assertEquals("four", out2.toString(), "Incorrect value");
     }
 
     @Test
     public void testNullConstructor() {
         final String testString = "foo";
         final AggregateTranslator subject = new AggregateTranslator((CharSequenceTranslator[]) null);
-        assertThat(subject.translate(testString)).isEqualTo(testString);
+        assertEquals(testString, subject.translate(testString));
     }
 
     @Test
     public void testNullVarargConstructor() {
         final String testString = "foo";
         final AggregateTranslator subject = new AggregateTranslator((CharSequenceTranslator) null);
-        assertThat(subject.translate(testString)).isEqualTo(testString);
+        assertEquals(testString, subject.translate(testString));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/translate/CodePointTranslatorTest.java b/src/test/java/org/apache/commons/text/translate/CodePointTranslatorTest.java
index e7fe55a0..56eb8b09 100644
--- a/src/test/java/org/apache/commons/text/translate/CodePointTranslatorTest.java
+++ b/src/test/java/org/apache/commons/text/translate/CodePointTranslatorTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.io.IOException;
 import java.io.PipedReader;
@@ -32,7 +32,7 @@ public class CodePointTranslatorTest {
         final UnicodeEscaper unicodeEscaper = new UnicodeEscaper();
         final String string = unicodeEscaper.toUtf16Escape(0);
         try (PipedReader pipedReader = new PipedReader(); PipedWriter pipedWriter = new PipedWriter(pipedReader)) {
-            assertThat(numericEntityEscaper.translate(string, 0, pipedWriter)).isEqualTo(1);
+            assertEquals(1, numericEntityEscaper.translate(string, 0, pipedWriter));
         }
     }
 
diff --git a/src/test/java/org/apache/commons/text/translate/CsvTranslatorsTest.java b/src/test/java/org/apache/commons/text/translate/CsvTranslatorsTest.java
index bf86136c..9804d5da 100644
--- a/src/test/java/org/apache/commons/text/translate/CsvTranslatorsTest.java
+++ b/src/test/java/org/apache/commons/text/translate/CsvTranslatorsTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.io.IOException;
 import java.io.StringWriter;
@@ -34,7 +34,7 @@ public class CsvTranslatorsTest {
         final String input = "hi,this,is,a,test";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(data).isEqualTo("\"hi,this,is,a,test\"");
+        assertEquals("\"hi,this,is,a,test\"", data);
     }
 
     @Test
@@ -44,7 +44,7 @@ public class CsvTranslatorsTest {
         final String input = "hi,this,is,a,CR,test" + String.valueOf(CharUtils.CR);
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(data).isEqualTo("\"hi,this,is,a,CR,test" + String.valueOf(CharUtils.CR) + "\"");
+        assertEquals("\"hi,this,is,a,CR,test" + String.valueOf(CharUtils.CR) + "\"", data);
     }
 
     @Test
@@ -54,7 +54,7 @@ public class CsvTranslatorsTest {
         final String input = "hi,this,is,a,LF,test" + String.valueOf(CharUtils.LF);
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(data).isEqualTo("\"hi,this,is,a,LF,test" + String.valueOf(CharUtils.LF) + "\"");
+        assertEquals("\"hi,this,is,a,LF,test" + String.valueOf(CharUtils.LF) + "\"", data);
     }
 
     @Test
@@ -64,7 +64,7 @@ public class CsvTranslatorsTest {
         final String input = "hi this is just a plane text nothing to do with csv!";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(input).isEqualTo(data);
+        assertEquals(data, input);
     }
 
     @Test
@@ -74,7 +74,7 @@ public class CsvTranslatorsTest {
         final String input = "hi,this,is,a,\"quote,test";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(data).isEqualTo("\"hi,this,is,a,\"\"quote,test\"");
+        assertEquals("\"hi,this,is,a,\"\"quote,test\"", data);
     }
 
     @Test
@@ -84,7 +84,7 @@ public class CsvTranslatorsTest {
         final String input = "hi,this,is,unescape,test";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(data).isEqualTo("hi,this,is,unescape,test");
+        assertEquals(input, data);
     }
 
     @Test
@@ -94,7 +94,7 @@ public class CsvTranslatorsTest {
         final String input = "\"hi,this,is,unescape,test\"";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(data).isEqualTo("hi,this,is,unescape,test");
+        assertEquals("hi,this,is,unescape,test", data);
     }
 
     @Test
@@ -104,7 +104,7 @@ public class CsvTranslatorsTest {
         final String input = "\"hi,this,is,unescape,test";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(input).isEqualTo(data);
+        assertEquals(input, data);
     }
 
     @Test
@@ -114,7 +114,7 @@ public class CsvTranslatorsTest {
         final String input = "hi,this,is,unescape,test\"";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(input).isEqualTo(data);
+        assertEquals(input, data);
     }
 
     @Test
@@ -124,7 +124,7 @@ public class CsvTranslatorsTest {
         final String input = "\"hi,this,is,\"unescape,test\"";
         escaper.translateWhole(input, writer);
         final String data = writer.toString();
-        assertThat(data).isEqualTo("hi,this,is,\"unescape,test");
+        assertEquals("hi,this,is,\"unescape,test", data);
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/translate/EntityArraysTest.java b/src/test/java/org/apache/commons/text/translate/EntityArraysTest.java
index e05d9768..991ce292 100644
--- a/src/test/java/org/apache/commons/text/translate/EntityArraysTest.java
+++ b/src/test/java/org/apache/commons/text/translate/EntityArraysTest.java
@@ -17,7 +17,7 @@
 
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.io.BufferedReader;
 import java.io.FileReader;
@@ -49,7 +49,7 @@ public class EntityArraysTest {
         for (final CharSequence escapeKey : escapeMap.keySet()) {
             for (final CharSequence unescapeKey : unescapeMap.keySet()) {
                 if (escapeKey == unescapeMap.get(unescapeKey)) {
-                    assertThat(unescapeKey).isEqualTo(escapeMap.get(escapeKey));
+                    assertEquals(escapeMap.get(escapeKey), unescapeKey);
                 }
             }
         }
@@ -74,7 +74,7 @@ public class EntityArraysTest {
                     final Map<String, String> mapValue = (Map<String, String>) EntityArrays.class.getDeclaredField(mapVariableName).get(EntityArrays.class);
                     // Validate that we are not inserting into the same key twice in the map declaration. If this,
                     // indeed was the case the keySet().size() would be smaller than the number of put() statements
-                    assertThat(mapValue.size()).isEqualTo(mapDeclarationCounter);
+                    assertEquals(mapDeclarationCounter, mapValue.size());
                 }
             }
         }
@@ -82,27 +82,27 @@ public class EntityArraysTest {
 
     @Test
     public void testForDuplicateDeclaredMapValuesAposMap() {
-        assertThat(EntityArrays.APOS_ESCAPE.keySet()).hasSameSizeAs(EntityArrays.APOS_UNESCAPE.keySet());
+        assertEquals(EntityArrays.APOS_UNESCAPE.keySet().size(), EntityArrays.APOS_ESCAPE.keySet().size());
     }
 
     @Test
     public void testForDuplicateDeclaredMapValuesBasicMap() {
-        assertThat(EntityArrays.BASIC_ESCAPE.keySet()).hasSameSizeAs(EntityArrays.BASIC_UNESCAPE.keySet());
+        assertEquals(EntityArrays.BASIC_ESCAPE.keySet().size(), EntityArrays.BASIC_UNESCAPE.keySet().size());
     }
 
     @Test
     public void testForDuplicateDeclaredMapValuesHtml40ExtendedMap() {
-        assertThat(EntityArrays.HTML40_EXTENDED_ESCAPE.keySet()).hasSameSizeAs(EntityArrays.HTML40_EXTENDED_UNESCAPE.keySet());
+        assertEquals(EntityArrays.HTML40_EXTENDED_ESCAPE.keySet().size(), EntityArrays.HTML40_EXTENDED_UNESCAPE.keySet().size());
     }
 
     @Test
     public void testForDuplicateDeclaredMapValuesISO8859Map() {
-        assertThat(EntityArrays.ISO8859_1_ESCAPE.keySet()).hasSameSizeAs(EntityArrays.ISO8859_1_UNESCAPE.keySet());
+        assertEquals(EntityArrays.ISO8859_1_ESCAPE.keySet().size(), EntityArrays.ISO8859_1_UNESCAPE.keySet().size());
     }
 
     @Test
     public void testForDuplicateDeclaredMapValuesJavaCtrlCharsMap() {
-        assertThat(EntityArrays.JAVA_CTRL_CHARS_ESCAPE.keySet()).hasSameSizeAs(EntityArrays.JAVA_CTRL_CHARS_UNESCAPE.keySet());
+        assertEquals(EntityArrays.JAVA_CTRL_CHARS_ESCAPE.keySet().size(), EntityArrays.JAVA_CTRL_CHARS_UNESCAPE.keySet().size());
     }
 
     @Test
diff --git a/src/test/java/org/apache/commons/text/translate/JavaUnicodeEscaperTest.java b/src/test/java/org/apache/commons/text/translate/JavaUnicodeEscaperTest.java
index 98a6a9a5..021e7828 100644
--- a/src/test/java/org/apache/commons/text/translate/JavaUnicodeEscaperTest.java
+++ b/src/test/java/org/apache/commons/text/translate/JavaUnicodeEscaperTest.java
@@ -16,7 +16,7 @@
  */
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import org.junit.jupiter.api.Test;
 
@@ -28,31 +28,25 @@ public class JavaUnicodeEscaperTest {
     @Test
     public void testAbove() {
         final JavaUnicodeEscaper jue = JavaUnicodeEscaper.above('F');
-
         final String input = "ADFGZ";
         final String result = jue.translate(input);
-        assertThat(result).as("Failed to escape Unicode characters via the above method")
-            .isEqualTo("ADF\\u0047\\u005A");
+        assertEquals("ADF\\u0047\\u005A", result, "Failed to escape Unicode characters via the above method");
     }
 
     @Test
     public void testBelow() {
         final JavaUnicodeEscaper jue = JavaUnicodeEscaper.below('F');
-
         final String input = "ADFGZ";
         final String result = jue.translate(input);
-        assertThat(result).as("Failed to escape Unicode characters via the below method")
-            .isEqualTo("\\u0041\\u0044FGZ");
+        assertEquals("\\u0041\\u0044FGZ", result, "Failed to escape Unicode characters via the below method");
     }
 
     @Test
     public void testBetween() {
         final JavaUnicodeEscaper jue = JavaUnicodeEscaper.between('F', 'L');
-
         final String input = "ADFGZ";
         final String result = jue.translate(input);
-        assertThat(result).as("Failed to escape Unicode characters via the between method")
-            .isEqualTo("AD\\u0046\\u0047Z");
+        assertEquals("AD\\u0046\\u0047Z", result, "Failed to escape Unicode characters via the between method");
     }
 
     @Test
@@ -62,6 +56,6 @@ public class JavaUnicodeEscaperTest {
         // Character ?, U+24B62, Binary Code Point 0010 0100 1011 0110 0010,
         // Binary UTF-167 1101 1000 0101 0010 1101 1111 0110 0010, UTF-16 Hex Code Units D852 DF62
         final String encoding = jue.toUtf16Escape(Integer.parseInt("024B62", 16));
-        assertThat(encoding).isEqualTo("\\uD852\\uDF62");
+        assertEquals("\\uD852\\uDF62", encoding);
     }
 }
diff --git a/src/test/java/org/apache/commons/text/translate/LookupTranslatorTest.java b/src/test/java/org/apache/commons/text/translate/LookupTranslatorTest.java
index 548434ff..1176c9bf 100644
--- a/src/test/java/org/apache/commons/text/translate/LookupTranslatorTest.java
+++ b/src/test/java/org/apache/commons/text/translate/LookupTranslatorTest.java
@@ -17,8 +17,8 @@
 
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrowsExactly;
 
 import java.io.IOException;
 import java.io.StringWriter;
@@ -40,13 +40,13 @@ public class LookupTranslatorTest  {
         final LookupTranslator lt = new LookupTranslator(translatorMap);
         final StringWriter out = new StringWriter();
         final int result = lt.translate("one", 0, out);
-        assertThat(result).as("Incorrect code point consumption").isEqualTo(3);
-        assertThat(out.toString()).as("Incorrect value").isEqualTo("two");
+        assertEquals(3, result, "Incorrect code point consumption");
+        assertEquals("two", out.toString(), "Incorrect value");
     }
 
     @Test
     public void testFailsToCreateLookupTranslatorThrowsInvalidParameterException() {
-        assertThatExceptionOfType(InvalidParameterException.class).isThrownBy(() -> new LookupTranslator(null));
+        assertThrowsExactly(InvalidParameterException.class, () -> new LookupTranslator(null));
     }
 
     // Tests: https://issues.apache.org/jira/browse/LANG-882
@@ -57,8 +57,8 @@ public class LookupTranslatorTest  {
         final LookupTranslator lt = new LookupTranslator(translatorMap);
         final StringWriter out = new StringWriter();
         final int result = lt.translate(new StringBuffer("one"), 0, out);
-        assertThat(result).as("Incorrect code point consumption").isEqualTo(3);
-        assertThat(out.toString()).as("Incorrect value").isEqualTo("two");
+        assertEquals(3, result, "Incorrect code point consumption");
+        assertEquals("two", out.toString(), "Incorrect value");
     }
 
     @Test
@@ -71,7 +71,7 @@ public class LookupTranslatorTest  {
         final LookupTranslator translator = new LookupTranslator(map);
         final String translated = translator.translate(symbol + "=A");
         /* we should get "A=A". */
-        assertThat(translated).as("Incorrect value").isEqualTo("A=A");
+        assertEquals("A=A", translated, "Incorrect value");
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/translate/NumericEntityEscaperTest.java b/src/test/java/org/apache/commons/text/translate/NumericEntityEscaperTest.java
index ff0cddf0..83275fe5 100644
--- a/src/test/java/org/apache/commons/text/translate/NumericEntityEscaperTest.java
+++ b/src/test/java/org/apache/commons/text/translate/NumericEntityEscaperTest.java
@@ -17,7 +17,7 @@
 
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import org.junit.jupiter.api.Test;
 
@@ -32,7 +32,7 @@ public class NumericEntityEscaperTest  {
 
         final String input = "ADFGZ";
         final String result = nee.translate(input);
-        assertThat(result).as("Failed to escape numeric entities via the above method").isEqualTo("ADF&#71;&#90;");
+        assertEquals("ADF&#71;&#90;", result, "Failed to escape numeric entities via the above method");
     }
 
     @Test
@@ -41,16 +41,15 @@ public class NumericEntityEscaperTest  {
 
         final String input = "ADFGZ";
         final String result = nee.translate(input);
-        assertThat(result).as("Failed to escape numeric entities via the below method").isEqualTo("&#65;&#68;FGZ");
+        assertEquals("&#65;&#68;FGZ", result, "Failed to escape numeric entities via the below method");
     }
 
     @Test
     public void testBetween() {
         final NumericEntityEscaper nee = NumericEntityEscaper.between('F', 'L');
-
         final String input = "ADFGZ";
         final String result = nee.translate(input);
-        assertThat(result).as("Failed to escape numeric entities via the between method").isEqualTo("AD&#70;&#71;Z");
+        assertEquals("AD&#70;&#71;Z", result, "Failed to escape numeric entities via the between method");
     }
 
     /** See LANG-617 */
@@ -59,9 +58,8 @@ public class NumericEntityEscaperTest  {
         final NumericEntityEscaper nee = new NumericEntityEscaper();
         final String input = "\uD803\uDC22";
         final String expected = "&#68642;";
-
         final String result = nee.translate(input);
-        assertThat(result).as("Failed to escape numeric entities supplementary characters").isEqualTo(expected);
+        assertEquals(expected, result, "Failed to escape numeric entities supplementary characters");
 
     }
 
diff --git a/src/test/java/org/apache/commons/text/translate/NumericEntityUnescaperTest.java b/src/test/java/org/apache/commons/text/translate/NumericEntityUnescaperTest.java
index 5e9e86ec..997d7332 100644
--- a/src/test/java/org/apache/commons/text/translate/NumericEntityUnescaperTest.java
+++ b/src/test/java/org/apache/commons/text/translate/NumericEntityUnescaperTest.java
@@ -17,8 +17,8 @@
 
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.fail;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import org.junit.jupiter.api.Test;
 
@@ -32,8 +32,7 @@ public class NumericEntityUnescaperTest  {
         final NumericEntityUnescaper.OPTION[] numericEntityUnescaperOPTIONArray = {};
         final NumericEntityUnescaper numericEntityUnescaper =
                 new NumericEntityUnescaper(numericEntityUnescaperOPTIONArray);
-
-        assertThat(numericEntityUnescaper.translate("2|y|O7y`&#uVWj")).isEqualTo("2|y|O7y`&#uVWj");
+        assertEquals("2|y|O7y`&#uVWj", numericEntityUnescaper.translate("2|y|O7y`&#uVWj"));
     }
 
     @Test
@@ -41,18 +40,17 @@ public class NumericEntityUnescaperTest  {
         final NumericEntityUnescaper.OPTION[] numericEntityUnescaperOPTIONArray = {};
         final NumericEntityUnescaper numericEntityUnescaper =
                 new NumericEntityUnescaper(numericEntityUnescaperOPTIONArray);
-
-        assertThat(numericEntityUnescaper.translate("Ws2v8|O=7NR&#cB")).isEqualTo("Ws2v8|O=7NR&#cB");
+        assertEquals("Ws2v8|O=7NR&#cB", numericEntityUnescaper.translate("Ws2v8|O=7NR&#cB"));
     }
 
     @Test
     public void testOutOfBounds() {
         final NumericEntityUnescaper neu = new NumericEntityUnescaper();
 
-        assertThat(neu.translate("Test &")).as("Failed to ignore when last character is &").isEqualTo("Test &");
-        assertThat(neu.translate("Test &#")).as("Failed to ignore when last character is &").isEqualTo("Test &#");
-        assertThat(neu.translate("Test &#x")).as("Failed to ignore when last character is &").isEqualTo("Test &#x");
-        assertThat(neu.translate("Test &#X")).as("Failed to ignore when last character is &").isEqualTo("Test &#X");
+        assertEquals("Test &", neu.translate("Test &"), "Failed to ignore when last character is &");
+        assertEquals("Test &#", neu.translate("Test &#"), "Failed to ignore when last character is &");
+        assertEquals("Test &#x", neu.translate("Test &#x"), "Failed to ignore when last character is &");
+        assertEquals("Test &#X", neu.translate("Test &#X"), "Failed to ignore when last character is &");
     }
 
     @Test
@@ -62,7 +60,7 @@ public class NumericEntityUnescaperTest  {
         final String expected = "\uD803\uDC22";
 
         final String result = neu.translate(input);
-        assertThat(result).as("Failed to unescape numeric entities supplementary characters").isEqualTo(expected);
+        assertEquals(expected, result, "Failed to unescape numeric entities supplementary characters");
     }
 
     @Test
@@ -73,7 +71,7 @@ public class NumericEntityUnescaperTest  {
         String expected = "Test \u0030 not test";
 
         String result = neu.translate(input);
-        assertThat(result).as("Failed to support unfinished entities (i.e. missing semicolon)").isEqualTo(expected);
+        assertEquals(expected, result, "Failed to support unfinished entities (i.e. missing semicolon)");
 
         // ignore it
         neu = new NumericEntityUnescaper();
@@ -81,7 +79,7 @@ public class NumericEntityUnescaperTest  {
         expected = input;
 
         result = neu.translate(input);
-        assertThat(result).as("Failed to ignore unfinished entities (i.e. missing semicolon)").isEqualTo(expected);
+        assertEquals(expected, result, "Failed to ignore unfinished entities (i.e. missing semicolon)");
 
         // fail it
         neu = new NumericEntityUnescaper(NumericEntityUnescaper.OPTION.errorIfNoSemiColon);
diff --git a/src/test/java/org/apache/commons/text/translate/OctalUnescaperTest.java b/src/test/java/org/apache/commons/text/translate/OctalUnescaperTest.java
index a6f60ad4..64b76c11 100644
--- a/src/test/java/org/apache/commons/text/translate/OctalUnescaperTest.java
+++ b/src/test/java/org/apache/commons/text/translate/OctalUnescaperTest.java
@@ -17,7 +17,7 @@
 
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import org.junit.jupiter.api.Test;
 
@@ -28,56 +28,55 @@ public class OctalUnescaperTest {
 
     @Test
     public void testBetween() {
-        final OctalUnescaper oue = new OctalUnescaper();   //.between("1", "377");
+        final OctalUnescaper oue = new OctalUnescaper(); // .between("1", "377");
 
         String input = "\\45";
         String result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\45");
+        assertEquals("\45", result, "Failed to unescape octal characters via the between method");
 
         input = "\\377";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\377");
+        assertEquals("\377", result, "Failed to unescape octal characters via the between method");
 
         input = "\\377 and";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\377 and");
+        assertEquals("\377 and", result, "Failed to unescape octal characters via the between method");
 
         input = "\\378 and";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\37" + "8 and");
+        assertEquals("\37" + "8 and", result, "Failed to unescape octal characters via the between method");
 
         input = "\\378";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\37" + "8");
+        assertEquals("\37" + "8", result, "Failed to unescape octal characters via the between method");
 
         input = "\\1";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\1");
+        assertEquals("\1", result, "Failed to unescape octal characters via the between method");
 
         input = "\\036";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\036");
+        assertEquals("\036", result, "Failed to unescape octal characters via the between method");
 
         input = "\\0365";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\036" + "5");
+        assertEquals("\036" + "5", result, "Failed to unescape octal characters via the between method");
 
         input = "\\003";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\003");
+        assertEquals("\003", result, "Failed to unescape octal characters via the between method");
 
         input = "\\0003";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\000" + "3");
+        assertEquals("\000" + "3", result, "Failed to unescape octal characters via the between method");
 
         input = "\\279";
         result = oue.translate(input);
-        assertThat(result).as("Failed to unescape octal characters via the between method").isEqualTo("\279");
+        assertEquals("\279", result, "Failed to unescape octal characters via the between method");
 
         input = "\\999";
         result = oue.translate(input);
-        assertThat(result).as("Failed to ignore an out of range octal character via the between method")
-            .isEqualTo("\\999");
+        assertEquals("\\999", result, "Failed to ignore an out of range octal character via the between method");
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/translate/SinglePassTranslatorTest.java b/src/test/java/org/apache/commons/text/translate/SinglePassTranslatorTest.java
index f6ca1c34..39aafd15 100644
--- a/src/test/java/org/apache/commons/text/translate/SinglePassTranslatorTest.java
+++ b/src/test/java/org/apache/commons/text/translate/SinglePassTranslatorTest.java
@@ -16,8 +16,8 @@
  */
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.io.IOException;
 import java.io.StringWriter;
@@ -48,19 +48,19 @@ public class SinglePassTranslatorTest {
 
     @Test
     public void testCodePointsAreReturned() throws Exception {
-        assertThat(dummyTranslator.translate("", 0, out)).isEqualTo(0);
-        assertThat(dummyTranslator.translate("abc", 0, out)).isEqualTo(3);
-        assertThat(dummyTranslator.translate("abcdefg", 0, out)).isEqualTo(7);
+        assertEquals(0, dummyTranslator.translate("", 0, out));
+        assertEquals(3, dummyTranslator.translate("abc", 0, out));
+        assertEquals(7, dummyTranslator.translate("abcdefg", 0, out));
     }
 
     @Test
     public void testIndexIsValidated() {
-        assertThatIllegalArgumentException().isThrownBy(() -> dummyTranslator.translate("abc", 1, out));
+        assertThrows(IllegalArgumentException.class, () -> dummyTranslator.translate("abc", 1, out));
     }
 
     @Test
     public void testTranslateThrowsIllegalArgumentException() {
-        assertThatIllegalArgumentException().isThrownBy(() -> dummyTranslator.translate("(,Fk", 647, null));
+        assertThrows(IllegalArgumentException.class, () -> dummyTranslator.translate("(,Fk", 647, null));
     }
 
 }
diff --git a/src/test/java/org/apache/commons/text/translate/UnicodeEscaperTest.java b/src/test/java/org/apache/commons/text/translate/UnicodeEscaperTest.java
index 6e0f9b12..3d06c57f 100644
--- a/src/test/java/org/apache/commons/text/translate/UnicodeEscaperTest.java
+++ b/src/test/java/org/apache/commons/text/translate/UnicodeEscaperTest.java
@@ -17,42 +17,36 @@
 
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import org.junit.jupiter.api.Test;
 
 /**
  * Tests {@link UnicodeEscaper}.
  */
-public class UnicodeEscaperTest  {
+public class UnicodeEscaperTest {
 
     @Test
     public void testAbove() {
-        final UnicodeEscaper ue = UnicodeEscaper.above('F');
-
+        final UnicodeEscaper escaper = UnicodeEscaper.above('F');
         final String input = "ADFGZ";
-        final String result = ue.translate(input);
-        assertThat(result).as("Failed to escape Unicode characters via the above method")
-            .isEqualTo("ADF\\u0047\\u005A");
+        final String result = escaper.translate(input);
+        assertEquals("ADF\\u0047\\u005A", result, "Failed to escape Unicode characters via the above method");
     }
 
     @Test
     public void testBelow() {
-        final UnicodeEscaper ue = UnicodeEscaper.below('F');
-
+        final UnicodeEscaper escaper = UnicodeEscaper.below('F');
         final String input = "ADFGZ";
-        final String result = ue.translate(input);
-        assertThat(result).as("Failed to escape Unicode characters via the below method")
-            .isEqualTo("\\u0041\\u0044FGZ");
+        final String result = escaper.translate(input);
+        assertEquals("\\u0041\\u0044FGZ", result, "Failed to escape Unicode characters via the below method");
     }
 
     @Test
     public void testBetween() {
-        final UnicodeEscaper ue = UnicodeEscaper.between('F', 'L');
-
+        final UnicodeEscaper escaper = UnicodeEscaper.between('F', 'L');
         final String input = "ADFGZ";
-        final String result = ue.translate(input);
-        assertThat(result).as("Failed to escape Unicode characters via the between method")
-            .isEqualTo("AD\\u0046\\u0047Z");
+        final String result = escaper.translate(input);
+        assertEquals("AD\\u0046\\u0047Z", result, "Failed to escape Unicode characters via the between method");
     }
 }
diff --git a/src/test/java/org/apache/commons/text/translate/UnicodeUnescaperTest.java b/src/test/java/org/apache/commons/text/translate/UnicodeUnescaperTest.java
index 4a729941..3653ae33 100644
--- a/src/test/java/org/apache/commons/text/translate/UnicodeUnescaperTest.java
+++ b/src/test/java/org/apache/commons/text/translate/UnicodeUnescaperTest.java
@@ -17,7 +17,7 @@
 
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
@@ -29,27 +29,24 @@ public class UnicodeUnescaperTest {
 
     @Test
     public void testLessThanFour() {
-        final UnicodeUnescaper uu = new UnicodeUnescaper();
-
+        final UnicodeUnescaper escaper = new UnicodeUnescaper();
         final String input = "\\0047\\u006";
-        assertThrows(IllegalArgumentException.class, () -> uu.translate(input));
+        assertThrows(IllegalArgumentException.class, () -> escaper.translate(input));
     }
 
     // Requested in LANG-507
     @Test
     public void testUPlus() {
-        final UnicodeUnescaper uu = new UnicodeUnescaper();
-
+        final UnicodeUnescaper escaper = new UnicodeUnescaper();
         final String input = "\\u+0047";
-        assertThat(uu.translate(input)).as("Failed to unescape Unicode characters with 'u+' notation").isEqualTo("G");
+        assertEquals("G", escaper.translate(input), "Failed to unescape Unicode characters with 'u+' notation");
     }
 
     @Test
     public void testUuuuu() {
-        final UnicodeUnescaper uu = new UnicodeUnescaper();
-
+        final UnicodeUnescaper escaper = new UnicodeUnescaper();
         final String input = "\\uuuuuuuu0047";
-        final String result = uu.translate(input);
-        assertThat(result).as("Failed to unescape Unicode characters with many 'u' characters").isEqualTo("G");
+        final String result = escaper.translate(input);
+        assertEquals("G", result, "Failed to unescape Unicode characters with many 'u' characters");
     }
 }
diff --git a/src/test/java/org/apache/commons/text/translate/UnicodeUnpairedSurrogateRemoverTest.java b/src/test/java/org/apache/commons/text/translate/UnicodeUnpairedSurrogateRemoverTest.java
index 20e3c8e5..cd3e8580 100644
--- a/src/test/java/org/apache/commons/text/translate/UnicodeUnpairedSurrogateRemoverTest.java
+++ b/src/test/java/org/apache/commons/text/translate/UnicodeUnpairedSurrogateRemoverTest.java
@@ -16,7 +16,9 @@
  */
 package org.apache.commons.text.translate;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.CharArrayWriter;
 import java.io.IOException;
@@ -32,16 +34,16 @@ public class UnicodeUnpairedSurrogateRemoverTest {
 
     @Test
     public void testInvalidCharacters() throws IOException {
-        assertThat(subject.translate(0xd800, writer)).isTrue();
-        assertThat(subject.translate(0xdfff, writer)).isTrue();
-        assertThat(writer.size()).isZero();
+        assertTrue(subject.translate(0xd800, writer));
+        assertTrue(subject.translate(0xdfff, writer));
+        assertEquals(0, writer.size());
     }
 
     @Test
     public void testValidCharacters() throws IOException {
-        assertThat(subject.translate(0xd7ff, writer)).isFalse();
-        assertThat(subject.translate(0xe000, writer)).isFalse();
-        assertThat(writer.size()).isZero();
+        assertFalse(subject.translate(0xd7ff, writer));
+        assertFalse(subject.translate(0xe000, writer));
+        assertEquals(0, writer.size());
     }
 }