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Posted to commits@kafka.apache.org by vv...@apache.org on 2020/08/26 02:11:33 UTC

[kafka] 01/01: Convert test-utils and StateStore

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

vvcephei pushed a commit to branch kip-478-part-4
in repository https://gitbox.apache.org/repos/asf/kafka.git

commit eb55d70adadc0c692d29a4c23d039131ae2f1f80
Author: John Roesler <vv...@apache.org>
AuthorDate: Tue Aug 25 19:29:00 2020 -0500

    Convert test-utils and StateStore
---
 .../examples/wordcount/WordCountProcessorDemo.java |  21 +-
 .../examples/wordcount/WordCountProcessorTest.java |  10 +-
 .../apache/kafka/streams/processor/StateStore.java |  32 +-
 ...=> InternalProcessorContextReverseAdapter.java} |   6 +-
 .../processor/internals/ProcessorAdapter.java      |   2 +-
 .../internals/ProcessorContextAdapter.java         |   4 +-
 .../internals/ProcessorContextReverseAdapter.java  | 129 ++---
 .../internals/GlobalProcessorContextImplTest.java  |  11 +-
 .../internals/ProcessorContextImplTest.java        |   2 +-
 .../processor/api/MockProcessorContext.java        | 546 +++++++++++++++++++++
 .../kafka/streams/MockApiProcessorContextTest.java | 405 +++++++++++++++
 11 files changed, 1040 insertions(+), 128 deletions(-)

diff --git a/streams/examples/src/main/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorDemo.java b/streams/examples/src/main/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorDemo.java
index c3f47da..a6a9b8a 100644
--- a/streams/examples/src/main/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorDemo.java
+++ b/streams/examples/src/main/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorDemo.java
@@ -22,9 +22,9 @@ import org.apache.kafka.streams.KafkaStreams;
 import org.apache.kafka.streams.KeyValue;
 import org.apache.kafka.streams.StreamsConfig;
 import org.apache.kafka.streams.Topology;
-import org.apache.kafka.streams.processor.Processor;
-import org.apache.kafka.streams.processor.ProcessorContext;
-import org.apache.kafka.streams.processor.ProcessorSupplier;
+import org.apache.kafka.streams.processor.api.Processor;
+import org.apache.kafka.streams.processor.api.ProcessorContext;
+import org.apache.kafka.streams.processor.api.ProcessorSupplier;
 import org.apache.kafka.streams.processor.PunctuationType;
 import org.apache.kafka.streams.state.KeyValueIterator;
 import org.apache.kafka.streams.state.KeyValueStore;
@@ -54,17 +54,17 @@ import java.util.concurrent.CountDownLatch;
  */
 public final class WordCountProcessorDemo {
 
-    static class MyProcessorSupplier implements ProcessorSupplier<String, String> {
+    static class MyProcessorSupplier implements ProcessorSupplier<String, String, String, String> {
 
         @Override
-        public Processor<String, String> get() {
-            return new Processor<String, String>() {
-                private ProcessorContext context;
+        public Processor<String, String, String, String> get() {
+            return new Processor<String, String, String, String>() {
+                private ProcessorContext<String, String> context;
                 private KeyValueStore<String, Integer> kvStore;
 
                 @Override
                 @SuppressWarnings("unchecked")
-                public void init(final ProcessorContext context) {
+                public void init(final ProcessorContext<String, String> context) {
                     this.context = context;
                     this.context.schedule(Duration.ofSeconds(1), PunctuationType.STREAM_TIME, timestamp -> {
                         try (final KeyValueIterator<String, Integer> iter = kvStore.all()) {
@@ -79,7 +79,7 @@ public final class WordCountProcessorDemo {
                             }
                         }
                     });
-                    this.kvStore = (KeyValueStore<String, Integer>) context.getStateStore("Counts");
+                    this.kvStore = context.getStateStore("Counts");
                 }
 
                 @Override
@@ -96,9 +96,6 @@ public final class WordCountProcessorDemo {
                         }
                     }
                 }
-
-                @Override
-                public void close() {}
             };
         }
     }
diff --git a/streams/examples/src/test/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorTest.java b/streams/examples/src/test/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorTest.java
index bec77e6..5ddda08 100644
--- a/streams/examples/src/test/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorTest.java
+++ b/streams/examples/src/test/java/org/apache/kafka/streams/examples/wordcount/WordCountProcessorTest.java
@@ -18,8 +18,8 @@ package org.apache.kafka.streams.examples.wordcount;
 
 import org.apache.kafka.common.serialization.Serdes;
 import org.apache.kafka.streams.KeyValue;
-import org.apache.kafka.streams.processor.MockProcessorContext;
-import org.apache.kafka.streams.processor.Processor;
+import org.apache.kafka.streams.processor.api.MockProcessorContext;
+import org.apache.kafka.streams.processor.api.Processor;
 import org.apache.kafka.streams.state.KeyValueStore;
 import org.apache.kafka.streams.state.Stores;
 import org.junit.Test;
@@ -36,7 +36,7 @@ import static org.junit.Assert.assertTrue;
 public class WordCountProcessorTest {
     @Test
     public void test() {
-        final MockProcessorContext context = new MockProcessorContext();
+        final MockProcessorContext<String, String> context = new MockProcessorContext<>();
 
         // Create, initialize, and register the state store.
         final KeyValueStore<String, Integer> store =
@@ -48,7 +48,7 @@ public class WordCountProcessorTest {
         context.register(store, null);
 
         // Create and initialize the processor under test
-        final Processor<String, String> processor = new WordCountProcessorDemo.MyProcessorSupplier().get();
+        final Processor<String, String, String, String> processor = new WordCountProcessorDemo.MyProcessorSupplier().get();
         processor.init(context);
 
         // send a record to the processor
@@ -61,7 +61,7 @@ public class WordCountProcessorTest {
         context.scheduledPunctuators().get(0).getPunctuator().punctuate(0L);
 
         // finally, we can verify the output.
-        final Iterator<MockProcessorContext.CapturedForward> capturedForwards = context.forwarded().iterator();
+        final Iterator<MockProcessorContext.CapturedForward<String, String>> capturedForwards = context.forwarded().iterator();
         assertEquals(new KeyValue<>("alpha", "2"), capturedForwards.next().keyValue());
         assertEquals(new KeyValue<>("beta", "1"), capturedForwards.next().keyValue());
         assertEquals(new KeyValue<>("gamma", "1"), capturedForwards.next().keyValue());
diff --git a/streams/src/main/java/org/apache/kafka/streams/processor/StateStore.java b/streams/src/main/java/org/apache/kafka/streams/processor/StateStore.java
index df53ee2..d143f69 100644
--- a/streams/src/main/java/org/apache/kafka/streams/processor/StateStore.java
+++ b/streams/src/main/java/org/apache/kafka/streams/processor/StateStore.java
@@ -17,6 +17,8 @@
 package org.apache.kafka.streams.processor;
 
 import org.apache.kafka.streams.errors.StreamsException;
+import org.apache.kafka.streams.processor.internals.ProcessorContextReverseAdapter;
+import org.apache.kafka.streams.processor.api.ProcessorContext;
 
 /**
  * A storage engine for managing state maintained by a stream processor.
@@ -49,6 +51,27 @@ public interface StateStore {
      * Initializes this state store.
      * <p>
      * The implementation of this function must register the root store in the context via the
+     * {@link org.apache.kafka.streams.processor.ProcessorContext#register(StateStore, StateRestoreCallback)} function,
+     * where the first {@link StateStore} parameter should always be the passed-in {@code root} object, and
+     * the second parameter should be an object of user's implementation
+     * of the {@link StateRestoreCallback} interface used for restoring the state store from the changelog.
+     * <p>
+     * Note that if the state store engine itself supports bulk writes, users can implement another
+     * interface {@link BatchingStateRestoreCallback} which extends {@link StateRestoreCallback} to
+     * let users implement bulk-load restoration logic instead of restoring one record at a time.
+     * <p>
+     * This method is not called if {@link StateStore#init(ProcessorContext, org.apache.kafka.streams.processor.StateStore)}
+     * is implemented.
+     *
+     * @throws IllegalStateException If store gets registered after initialized is already finished
+     * @throws StreamsException if the store's change log does not contain the partition
+     */
+    void init(org.apache.kafka.streams.processor.ProcessorContext context, StateStore root);
+
+    /**
+     * Initializes this state store.
+     * <p>
+     * The implementation of this function must register the root store in the context via the
      * {@link ProcessorContext#register(StateStore, StateRestoreCallback)} function, where the
      * first {@link StateStore} parameter should always be the passed-in {@code root} object, and
      * the second parameter should be an object of user's implementation
@@ -61,7 +84,14 @@ public interface StateStore {
      * @throws IllegalStateException If store gets registered after initialized is already finished
      * @throws StreamsException if the store's change log does not contain the partition
      */
-    void init(ProcessorContext context, StateStore root);
+    default void init(final ProcessorContext<?, ?> context, final StateStore root) {
+        final org.apache.kafka.streams.processor.ProcessorContext adapted =
+            ProcessorContextReverseAdapter.adapt(
+                context,
+                new ProcessorContextReverseAdapter.UnsupportedDeprecatedForwarder()
+            );
+        init(adapted, root);
+    }
 
     /**
      * Flush any cached data
diff --git a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextReverseAdapter.java b/streams/src/main/java/org/apache/kafka/streams/processor/internals/InternalProcessorContextReverseAdapter.java
similarity index 96%
copy from streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextReverseAdapter.java
copy to streams/src/main/java/org/apache/kafka/streams/processor/internals/InternalProcessorContextReverseAdapter.java
index 6e82a5e..11fc1f9 100644
--- a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextReverseAdapter.java
+++ b/streams/src/main/java/org/apache/kafka/streams/processor/internals/InternalProcessorContextReverseAdapter.java
@@ -34,18 +34,18 @@ import java.io.File;
 import java.time.Duration;
 import java.util.Map;
 
-public final class ProcessorContextReverseAdapter implements InternalProcessorContext {
+public final class InternalProcessorContextReverseAdapter implements InternalProcessorContext {
     private final InternalApiProcessorContext<Object, Object> delegate;
 
     static InternalProcessorContext adapt(final InternalApiProcessorContext<Object, Object> delegate) {
         if (delegate instanceof ProcessorContextAdapter) {
             return ((ProcessorContextAdapter<Object, Object>) delegate).delegate();
         } else {
-            return new ProcessorContextReverseAdapter(delegate);
+            return new InternalProcessorContextReverseAdapter(delegate);
         }
     }
 
-    private ProcessorContextReverseAdapter(final InternalApiProcessorContext<Object, Object> delegate) {
+    private InternalProcessorContextReverseAdapter(final InternalApiProcessorContext<Object, Object> delegate) {
         this.delegate = delegate;
     }
 
diff --git a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorAdapter.java b/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorAdapter.java
index d8e4af4..3bbbe78 100644
--- a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorAdapter.java
+++ b/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorAdapter.java
@@ -47,7 +47,7 @@ public final class ProcessorAdapter<KIn, VIn, KOut, VOut> implements Processor<K
     @SuppressWarnings("unchecked")
     @Override
     public void init(final ProcessorContext<KOut, VOut> context) {
-        delegate.init(ProcessorContextReverseAdapter.adapt((InternalApiProcessorContext<Object, Object>) context));
+        delegate.init(InternalProcessorContextReverseAdapter.adapt((InternalApiProcessorContext<Object, Object>) context));
     }
 
     @Override
diff --git a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextAdapter.java b/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextAdapter.java
index 85dbd52..8d18ec7 100644
--- a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextAdapter.java
+++ b/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextAdapter.java
@@ -42,8 +42,8 @@ public final class ProcessorContextAdapter<KForward, VForward>
 
     @SuppressWarnings("unchecked")
     public static <KForward, VForward> InternalApiProcessorContext<KForward, VForward> adapt(final InternalProcessorContext delegate) {
-        if (delegate instanceof ProcessorContextReverseAdapter) {
-            return (InternalApiProcessorContext<KForward, VForward>) ((ProcessorContextReverseAdapter) delegate).delegate();
+        if (delegate instanceof InternalProcessorContextReverseAdapter) {
+            return (InternalApiProcessorContext<KForward, VForward>) ((InternalProcessorContextReverseAdapter) delegate).delegate();
         } else {
             return new ProcessorContextAdapter<>(delegate);
         }
diff --git a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextReverseAdapter.java b/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextReverseAdapter.java
index 6e82a5e..131b776 100644
--- a/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextReverseAdapter.java
+++ b/streams/src/main/java/org/apache/kafka/streams/processor/internals/ProcessorContextReverseAdapter.java
@@ -18,35 +18,52 @@ package org.apache.kafka.streams.processor.internals;
 
 import org.apache.kafka.common.header.Headers;
 import org.apache.kafka.common.serialization.Serde;
-import org.apache.kafka.common.utils.Bytes;
+import org.apache.kafka.streams.StreamsMetrics;
 import org.apache.kafka.streams.processor.Cancellable;
+import org.apache.kafka.streams.processor.api.ProcessorContext;
 import org.apache.kafka.streams.processor.PunctuationType;
 import org.apache.kafka.streams.processor.Punctuator;
 import org.apache.kafka.streams.processor.StateRestoreCallback;
 import org.apache.kafka.streams.processor.StateStore;
 import org.apache.kafka.streams.processor.TaskId;
 import org.apache.kafka.streams.processor.To;
-import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
-import org.apache.kafka.streams.state.StoreBuilder;
-import org.apache.kafka.streams.state.internals.ThreadCache;
 
 import java.io.File;
 import java.time.Duration;
 import java.util.Map;
 
-public final class ProcessorContextReverseAdapter implements InternalProcessorContext {
-    private final InternalApiProcessorContext<Object, Object> delegate;
+public final class ProcessorContextReverseAdapter implements org.apache.kafka.streams.processor.ProcessorContext {
+    private final ProcessorContext<Object, Object> delegate;
+    private final DeprecatedForwarder deprecatedForwarder;
 
-    static InternalProcessorContext adapt(final InternalApiProcessorContext<Object, Object> delegate) {
+    public interface DeprecatedForwarder {
+        <K, V> void forward(final K key, final V value, final int childIndex);
+    }
+
+    public static final class UnsupportedDeprecatedForwarder implements DeprecatedForwarder {
+        @Override
+        public <K, V> void forward(final K key, final V value, final int childIndex) {
+            throw new UnsupportedOperationException("Forwarding by index was deprecated in 2.0 and is not supported by this ProcessorContext.");
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    public static org.apache.kafka.streams.processor.ProcessorContext adapt(final ProcessorContext<?, ?> delegate,
+                                                                            final DeprecatedForwarder deprecatedForwarder) {
         if (delegate instanceof ProcessorContextAdapter) {
-            return ((ProcessorContextAdapter<Object, Object>) delegate).delegate();
+            return ((ProcessorContextAdapter<?, ?>) delegate).delegate();
+        } else if (delegate instanceof InternalApiProcessorContext) {
+            return InternalProcessorContextReverseAdapter.adapt((InternalApiProcessorContext<Object, Object>) delegate);
         } else {
-            return new ProcessorContextReverseAdapter(delegate);
+            return new ProcessorContextReverseAdapter(delegate, deprecatedForwarder);
         }
     }
 
-    private ProcessorContextReverseAdapter(final InternalApiProcessorContext<Object, Object> delegate) {
-        this.delegate = delegate;
+    @SuppressWarnings("unchecked")
+    private ProcessorContextReverseAdapter(final ProcessorContext<?, ?> delegate,
+                                           final DeprecatedForwarder deprecatedForwarder) {
+        this.delegate = (ProcessorContext<Object, Object>) delegate;
+        this.deprecatedForwarder = deprecatedForwarder;
     }
 
     @Override
@@ -75,91 +92,11 @@ public final class ProcessorContextReverseAdapter implements InternalProcessorCo
     }
 
     @Override
-    public StreamsMetricsImpl metrics() {
+    public StreamsMetrics metrics() {
         return delegate.metrics();
     }
 
     @Override
-    public void setSystemTimeMs(final long timeMs) {
-        delegate.setSystemTimeMs(timeMs);
-    }
-
-    @Override
-    public long currentSystemTimeMs() {
-        return delegate.currentSystemTimeMs();
-    }
-
-    @Override
-    public ProcessorRecordContext recordContext() {
-        return delegate.recordContext();
-    }
-
-    @Override
-    public void setRecordContext(final ProcessorRecordContext recordContext) {
-        delegate.setRecordContext(recordContext);
-    }
-
-    @Override
-    public void setCurrentNode(final ProcessorNode<?, ?, ?, ?> currentNode) {
-        delegate.setCurrentNode(currentNode);
-    }
-
-    @Override
-    public ProcessorNode<?, ?, ?, ?> currentNode() {
-        return delegate.currentNode();
-    }
-
-    @Override
-    public ThreadCache cache() {
-        return delegate.cache();
-    }
-
-    @Override
-    public void initialize() {
-        delegate.initialize();
-    }
-
-    @Override
-    public void uninitialize() {
-        delegate.uninitialize();
-    }
-
-    @Override
-    public Task.TaskType taskType() {
-        return delegate.taskType();
-    }
-
-    @Override
-    public void transitionToActive(final StreamTask streamTask, final RecordCollector recordCollector, final ThreadCache newCache) {
-        delegate.transitionToActive(streamTask, recordCollector, newCache);
-    }
-
-    @Override
-    public void transitionToStandby(final ThreadCache newCache) {
-        delegate.transitionToStandby(newCache);
-    }
-
-    @Override
-    public void registerCacheFlushListener(final String namespace, final ThreadCache.DirtyEntryFlushListener listener) {
-        delegate.registerCacheFlushListener(namespace, listener);
-    }
-
-    @Override
-    public <T extends StateStore> T getStateStore(final StoreBuilder<T> builder) {
-        return delegate.getStateStore(builder);
-    }
-
-    @Override
-    public void logChange(final String storeName, final Bytes key, final byte[] value, final long timestamp) {
-        delegate.logChange(storeName, key, value, timestamp);
-    }
-
-    @Override
-    public String changelogFor(final String storeName) {
-        return delegate.changelogFor(storeName);
-    }
-
-    @Override
     public void register(final StateStore store, final StateRestoreCallback stateRestoreCallback) {
         delegate.register(store, stateRestoreCallback);
     }
@@ -176,7 +113,7 @@ public final class ProcessorContextReverseAdapter implements InternalProcessorCo
     }
 
     @Override
-    public Cancellable schedule(final Duration interval, final PunctuationType type, final Punctuator callback) throws IllegalArgumentException {
+    public Cancellable schedule(final Duration interval, final PunctuationType type, final Punctuator callback) {
         return delegate.schedule(interval, type, callback);
     }
 
@@ -193,7 +130,7 @@ public final class ProcessorContextReverseAdapter implements InternalProcessorCo
     @Deprecated
     @Override
     public <K, V> void forward(final K key, final V value, final int childIndex) {
-        delegate.forward(key, value, To.child((currentNode().children()).get(childIndex).name()));
+        deprecatedForwarder.forward(key, value, childIndex);
     }
 
     @Deprecated
@@ -241,8 +178,4 @@ public final class ProcessorContextReverseAdapter implements InternalProcessorCo
     public Map<String, Object> appConfigsWithPrefix(final String prefix) {
         return delegate.appConfigsWithPrefix(prefix);
     }
-
-    InternalApiProcessorContext<Object, Object> delegate() {
-        return delegate;
-    }
 }
diff --git a/streams/src/test/java/org/apache/kafka/streams/processor/internals/GlobalProcessorContextImplTest.java b/streams/src/test/java/org/apache/kafka/streams/processor/internals/GlobalProcessorContextImplTest.java
index ad8cd0a..e180010 100644
--- a/streams/src/test/java/org/apache/kafka/streams/processor/internals/GlobalProcessorContextImplTest.java
+++ b/streams/src/test/java/org/apache/kafka/streams/processor/internals/GlobalProcessorContextImplTest.java
@@ -18,6 +18,7 @@ package org.apache.kafka.streams.processor.internals;
 
 import org.apache.kafka.common.serialization.Serdes;
 import org.apache.kafka.streams.StreamsConfig;
+import org.apache.kafka.streams.processor.ProcessorContext;
 import org.apache.kafka.streams.processor.StateStore;
 import org.apache.kafka.streams.processor.To;
 import org.apache.kafka.streams.processor.internals.Task.TaskType;
@@ -142,7 +143,7 @@ public class GlobalProcessorContextImplTest {
     public void shouldNotAllowInitForKeyValueStore() {
         final StateStore store = globalContext.getStateStore(GLOBAL_KEY_VALUE_STORE_NAME);
         try {
-            store.init(null, null);
+            store.init((ProcessorContext) null, null);
             fail("Should have thrown UnsupportedOperationException.");
         } catch (final UnsupportedOperationException expected) { }
     }
@@ -151,7 +152,7 @@ public class GlobalProcessorContextImplTest {
     public void shouldNotAllowInitForTimestampedKeyValueStore() {
         final StateStore store = globalContext.getStateStore(GLOBAL_TIMESTAMPED_KEY_VALUE_STORE_NAME);
         try {
-            store.init(null, null);
+            store.init((ProcessorContext) null, null);
             fail("Should have thrown UnsupportedOperationException.");
         } catch (final UnsupportedOperationException expected) { }
     }
@@ -160,7 +161,7 @@ public class GlobalProcessorContextImplTest {
     public void shouldNotAllowInitForWindowStore() {
         final StateStore store = globalContext.getStateStore(GLOBAL_WINDOW_STORE_NAME);
         try {
-            store.init(null, null);
+            store.init((ProcessorContext) null, null);
             fail("Should have thrown UnsupportedOperationException.");
         } catch (final UnsupportedOperationException expected) { }
     }
@@ -169,7 +170,7 @@ public class GlobalProcessorContextImplTest {
     public void shouldNotAllowInitForTimestampedWindowStore() {
         final StateStore store = globalContext.getStateStore(GLOBAL_TIMESTAMPED_WINDOW_STORE_NAME);
         try {
-            store.init(null, null);
+            store.init((ProcessorContext) null, null);
             fail("Should have thrown UnsupportedOperationException.");
         } catch (final UnsupportedOperationException expected) { }
     }
@@ -178,7 +179,7 @@ public class GlobalProcessorContextImplTest {
     public void shouldNotAllowInitForSessionStore() {
         final StateStore store = globalContext.getStateStore(GLOBAL_SESSION_STORE_NAME);
         try {
-            store.init(null, null);
+            store.init((ProcessorContext) null, null);
             fail("Should have thrown UnsupportedOperationException.");
         } catch (final UnsupportedOperationException expected) { }
     }
diff --git a/streams/src/test/java/org/apache/kafka/streams/processor/internals/ProcessorContextImplTest.java b/streams/src/test/java/org/apache/kafka/streams/processor/internals/ProcessorContextImplTest.java
index f4b62c3d..ab88efa 100644
--- a/streams/src/test/java/org/apache/kafka/streams/processor/internals/ProcessorContextImplTest.java
+++ b/streams/src/test/java/org/apache/kafka/streams/processor/internals/ProcessorContextImplTest.java
@@ -767,7 +767,7 @@ public class ProcessorContextImplTest {
         assertTrue(store.persistent());
         assertTrue(store.isOpen());
 
-        checkThrowsUnsupportedOperation(() -> store.init(null, null), "init()");
+        checkThrowsUnsupportedOperation(() -> store.init((ProcessorContext) null, null), "init()");
         checkThrowsUnsupportedOperation(store::close, "close()");
     }
 
diff --git a/streams/test-utils/src/main/java/org/apache/kafka/streams/processor/api/MockProcessorContext.java b/streams/test-utils/src/main/java/org/apache/kafka/streams/processor/api/MockProcessorContext.java
new file mode 100644
index 0000000..acad94d
--- /dev/null
+++ b/streams/test-utils/src/main/java/org/apache/kafka/streams/processor/api/MockProcessorContext.java
@@ -0,0 +1,546 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.processor.api;
+
+import org.apache.kafka.common.header.Headers;
+import org.apache.kafka.common.metrics.MetricConfig;
+import org.apache.kafka.common.metrics.Metrics;
+import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.serialization.Serde;
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.streams.KeyValue;
+import org.apache.kafka.streams.StreamsConfig;
+import org.apache.kafka.streams.StreamsMetrics;
+import org.apache.kafka.streams.Topology;
+import org.apache.kafka.streams.TopologyTestDriver;
+import org.apache.kafka.streams.internals.ApiUtils;
+import org.apache.kafka.streams.kstream.Transformer;
+import org.apache.kafka.streams.kstream.ValueTransformer;
+import org.apache.kafka.streams.processor.Cancellable;
+import org.apache.kafka.streams.processor.PunctuationType;
+import org.apache.kafka.streams.processor.Punctuator;
+import org.apache.kafka.streams.processor.StateRestoreCallback;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.TaskId;
+import org.apache.kafka.streams.processor.To;
+import org.apache.kafka.streams.processor.internals.ClientUtils;
+import org.apache.kafka.streams.processor.internals.RecordCollector;
+import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
+import org.apache.kafka.streams.processor.internals.metrics.TaskMetrics;
+import org.apache.kafka.streams.state.internals.InMemoryKeyValueStore;
+
+import java.io.File;
+import java.lang.reflect.Field;
+import java.time.Duration;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+
+import static org.apache.kafka.common.utils.Utils.mkEntry;
+import static org.apache.kafka.common.utils.Utils.mkMap;
+import static org.apache.kafka.common.utils.Utils.mkProperties;
+
+/**
+ * {@link MockProcessorContext} is a mock of {@link ProcessorContext} for users to test their {@link Processor},
+ * {@link Transformer}, and {@link ValueTransformer} implementations.
+ * <p>
+ * The tests for this class (org.apache.kafka.streams.MockProcessorContextTest) include several behavioral
+ * tests that serve as example usage.
+ * <p>
+ * Note that this class does not take any automated actions (such as firing scheduled punctuators).
+ * It simply captures any data it witnesses.
+ * If you require more automated tests, we recommend wrapping your {@link Processor} in a minimal source-processor-sink
+ * {@link Topology} and using the {@link TopologyTestDriver}.
+ */
+public class MockProcessorContext<KForward, VForward> implements ProcessorContext<KForward, VForward>, RecordCollector.Supplier {
+    // Immutable fields ================================================
+    private final StreamsMetricsImpl metrics;
+    private final TaskId taskId;
+    private final StreamsConfig config;
+    private final File stateDir;
+
+    // settable record metadata ================================================
+    private String topic;
+    private Integer partition;
+    private Long offset;
+    private Headers headers;
+    private Long timestamp;
+
+    // mocks ================================================
+    private final Map<String, StateStore> stateStores = new HashMap<>();
+    private final List<CapturedPunctuator> punctuators = new LinkedList<>();
+    private final List<CapturedForward<KForward, VForward>> capturedForwards = new LinkedList<>();
+    private boolean committed = false;
+
+
+    /**
+     * {@link CapturedPunctuator} holds captured punctuators, along with their scheduling information.
+     */
+    public static final class CapturedPunctuator {
+        private final long intervalMs;
+        private final PunctuationType type;
+        private final Punctuator punctuator;
+        private boolean cancelled = false;
+
+        private CapturedPunctuator(final long intervalMs, final PunctuationType type, final Punctuator punctuator) {
+            this.intervalMs = intervalMs;
+            this.type = type;
+            this.punctuator = punctuator;
+        }
+
+        @SuppressWarnings("unused")
+        public long getIntervalMs() {
+            return intervalMs;
+        }
+
+        @SuppressWarnings("unused")
+        public PunctuationType getType() {
+            return type;
+        }
+
+        @SuppressWarnings("unused")
+        public Punctuator getPunctuator() {
+            return punctuator;
+        }
+
+        @SuppressWarnings({"WeakerAccess", "unused"})
+        public void cancel() {
+            cancelled = true;
+        }
+
+        @SuppressWarnings("unused")
+        public boolean cancelled() {
+            return cancelled;
+        }
+    }
+
+    public static final class CapturedForward<KForward, VForward> {
+        private final String childName;
+        private final long timestamp;
+        private final KeyValue<KForward, VForward> keyValue;
+
+        private CapturedForward(final To to, final KeyValue<KForward, VForward> keyValue) {
+            if (keyValue == null) {
+                throw new IllegalArgumentException("keyValue can't be null");
+            }
+
+            try {
+                final Field field = To.class.getDeclaredField("childName");
+                field.setAccessible(true);
+                childName = (String) field.get(to);
+            } catch (final IllegalAccessException | NoSuchFieldException e) {
+                throw new RuntimeException(e);
+            }
+            timestamp = getTimestamp(to);
+
+            this.keyValue = keyValue;
+        }
+
+        /**
+         * The child this data was forwarded to.
+         *
+         * @return The child name, or {@code null} if it was broadcast.
+         */
+        @SuppressWarnings("unused")
+        public String childName() {
+            return childName;
+        }
+
+        /**
+         * The timestamp attached to the forwarded record.
+         *
+         * @return A timestamp, or {@code -1} if none was forwarded.
+         */
+        @SuppressWarnings("unused")
+        public long timestamp() {
+            return timestamp;
+        }
+
+        /**
+         * The data forwarded.
+         *
+         * @return A key/value pair. Not null.
+         */
+        @SuppressWarnings("unused")
+        public KeyValue<KForward, VForward> keyValue() {
+            return keyValue;
+        }
+
+        @Override
+        public String toString() {
+            return "CapturedForward{" +
+                "childName='" + childName + '\'' +
+                ", timestamp=" + timestamp +
+                ", keyValue=" + keyValue +
+                '}';
+        }
+    }
+
+    // constructors ================================================
+
+    /**
+     * Create a {@link MockProcessorContext} with dummy {@code config} and {@code taskId} and {@code null} {@code stateDir}.
+     * Most unit tests using this mock won't need to know the taskId,
+     * and most unit tests should be able to get by with the
+     * {@link InMemoryKeyValueStore}, so the stateDir won't matter.
+     */
+    @SuppressWarnings("unused")
+    public MockProcessorContext() {
+        this(
+            mkProperties(mkMap(
+                mkEntry(StreamsConfig.APPLICATION_ID_CONFIG, ""),
+                mkEntry(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "")
+            )),
+            new TaskId(0, 0),
+            null
+        );
+    }
+
+    /**
+     * Create a {@link MockProcessorContext} with dummy {@code taskId} and {@code null} {@code stateDir}.
+     * Most unit tests using this mock won't need to know the taskId,
+     * and most unit tests should be able to get by with the
+     * {@link InMemoryKeyValueStore}, so the stateDir won't matter.
+     *
+     * @param config a Properties object, used to configure the context and the processor.
+     */
+    @SuppressWarnings("unused")
+    public MockProcessorContext(final Properties config) {
+        this(config, new TaskId(0, 0), null);
+    }
+
+    /**
+     * Create a {@link MockProcessorContext} with a specified taskId and null stateDir.
+     *
+     * @param config   a {@link Properties} object, used to configure the context and the processor.
+     * @param taskId   a {@link TaskId}, which the context makes available via {@link MockProcessorContext#taskId()}.
+     * @param stateDir a {@link File}, which the context makes available viw {@link MockProcessorContext#stateDir()}.
+     */
+    @SuppressWarnings("unused")
+    public MockProcessorContext(final Properties config, final TaskId taskId, final File stateDir) {
+        final StreamsConfig streamsConfig = new ClientUtils.QuietStreamsConfig(config);
+        this.taskId = taskId;
+        this.config = streamsConfig;
+        this.stateDir = stateDir;
+        final MetricConfig metricConfig = new MetricConfig();
+        metricConfig.recordLevel(Sensor.RecordingLevel.DEBUG);
+        final String threadId = Thread.currentThread().getName();
+        metrics = new StreamsMetricsImpl(
+            new Metrics(metricConfig),
+            threadId,
+            streamsConfig.getString(StreamsConfig.BUILT_IN_METRICS_VERSION_CONFIG),
+            Time.SYSTEM
+        );
+        TaskMetrics.droppedRecordsSensorOrSkippedRecordsSensor(threadId, taskId.toString(), metrics);
+    }
+
+    @Override
+    public String applicationId() {
+        return config.getString(StreamsConfig.APPLICATION_ID_CONFIG);
+    }
+
+    @Override
+    public TaskId taskId() {
+        return taskId;
+    }
+
+    @Override
+    public Map<String, Object> appConfigs() {
+        final Map<String, Object> combined = new HashMap<>();
+        combined.putAll(config.originals());
+        combined.putAll(config.values());
+        return combined;
+    }
+
+    @Override
+    public Map<String, Object> appConfigsWithPrefix(final String prefix) {
+        return config.originalsWithPrefix(prefix);
+    }
+
+    @Override
+    public Serde<?> keySerde() {
+        return config.defaultKeySerde();
+    }
+
+    @Override
+    public Serde<?> valueSerde() {
+        return config.defaultValueSerde();
+    }
+
+    @Override
+    public File stateDir() {
+        return stateDir;
+    }
+
+    @Override
+    public StreamsMetrics metrics() {
+        return metrics;
+    }
+
+    // settable record metadata ================================================
+
+    /**
+     * The context exposes these metadata for use in the processor. Normally, they are set by the Kafka Streams framework,
+     * but for the purpose of driving unit tests, you can set them directly.
+     *
+     * @param topic     A topic name
+     * @param partition A partition number
+     * @param offset    A record offset
+     * @param timestamp A record timestamp
+     */
+    @SuppressWarnings("unused")
+    public void setRecordMetadata(final String topic,
+                                  final int partition,
+                                  final long offset,
+                                  final Headers headers,
+                                  final long timestamp) {
+        this.topic = topic;
+        this.partition = partition;
+        this.offset = offset;
+        this.headers = headers;
+        this.timestamp = timestamp;
+    }
+
+    /**
+     * The context exposes this metadata for use in the processor. Normally, they are set by the Kafka Streams framework,
+     * but for the purpose of driving unit tests, you can set it directly. Setting this attribute doesn't affect the others.
+     *
+     * @param topic A topic name
+     */
+    @SuppressWarnings("unused")
+    public void setTopic(final String topic) {
+        this.topic = topic;
+    }
+
+    /**
+     * The context exposes this metadata for use in the processor. Normally, they are set by the Kafka Streams framework,
+     * but for the purpose of driving unit tests, you can set it directly. Setting this attribute doesn't affect the others.
+     *
+     * @param partition A partition number
+     */
+    @SuppressWarnings("unused")
+    public void setPartition(final int partition) {
+        this.partition = partition;
+    }
+
+    /**
+     * The context exposes this metadata for use in the processor. Normally, they are set by the Kafka Streams framework,
+     * but for the purpose of driving unit tests, you can set it directly. Setting this attribute doesn't affect the others.
+     *
+     * @param offset A record offset
+     */
+    @SuppressWarnings("unused")
+    public void setOffset(final long offset) {
+        this.offset = offset;
+    }
+
+    /**
+     * The context exposes this metadata for use in the processor. Normally, they are set by the Kafka Streams framework,
+     * but for the purpose of driving unit tests, you can set it directly. Setting this attribute doesn't affect the others.
+     *
+     * @param headers Record headers
+     */
+    @SuppressWarnings("unused")
+    public void setHeaders(final Headers headers) {
+        this.headers = headers;
+    }
+
+    /**
+     * The context exposes this metadata for use in the processor. Normally, they are set by the Kafka Streams framework,
+     * but for the purpose of driving unit tests, you can set it directly. Setting this attribute doesn't affect the others.
+     *
+     * @param timestamp A record timestamp
+     */
+    @SuppressWarnings("unused")
+    public void setTimestamp(final long timestamp) {
+        this.timestamp = timestamp;
+    }
+
+    @Override
+    public String topic() {
+        if (topic == null) {
+            throw new IllegalStateException("Topic must be set before use via setRecordMetadata() or setTopic().");
+        }
+        return topic;
+    }
+
+    @Override
+    public int partition() {
+        if (partition == null) {
+            throw new IllegalStateException("Partition must be set before use via setRecordMetadata() or setPartition().");
+        }
+        return partition;
+    }
+
+    @Override
+    public long offset() {
+        if (offset == null) {
+            throw new IllegalStateException("Offset must be set before use via setRecordMetadata() or setOffset().");
+        }
+        return offset;
+    }
+
+    @Override
+    public Headers headers() {
+        return headers;
+    }
+
+    @Override
+    public long timestamp() {
+        if (timestamp == null) {
+            throw new IllegalStateException("Timestamp must be set before use via setRecordMetadata() or setTimestamp().");
+        }
+        return timestamp;
+    }
+
+    // mocks ================================================
+
+    @Override
+    public void register(final StateStore store,
+                         final StateRestoreCallback stateRestoreCallbackIsIgnoredInMock) {
+        stateStores.put(store.name(), store);
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public <S extends StateStore> S getStateStore(final String name) {
+        return (S) stateStores.get(name);
+    }
+
+    @Override
+    public Cancellable schedule(final Duration interval,
+                                final PunctuationType type,
+                                final Punctuator callback) {
+        final CapturedPunctuator capturedPunctuator =
+            new CapturedPunctuator(ApiUtils.validateMillisecondDuration(interval, "interval"), type, callback);
+
+        punctuators.add(capturedPunctuator);
+
+        return capturedPunctuator::cancel;
+    }
+
+    /**
+     * Get the punctuators scheduled so far. The returned list is not affected by subsequent calls to {@code schedule(...)}.
+     *
+     * @return A list of captured punctuators.
+     */
+    @SuppressWarnings("unused")
+    public List<CapturedPunctuator> scheduledPunctuators() {
+        return new LinkedList<>(punctuators);
+    }
+
+    @Override
+    public <K extends KForward, V extends VForward> void forward(final K key, final V value) {
+        forward(key, value, To.all());
+    }
+
+    @Override
+    public <K extends KForward, V extends VForward> void forward(final K key, final V value, final To to) {
+        capturedForwards.add(
+            new CapturedForward<>(
+                (getTimestamp(to)) == -1 ? to.withTimestamp(timestamp == null ? -1 : timestamp) : to,
+                new KeyValue<>(key, value)
+            )
+        );
+    }
+
+    /**
+     * Get all the forwarded data this context has observed. The returned list will not be
+     * affected by subsequent interactions with the context. The data in the list is in the same order as the calls to
+     * {@code forward(...)}.
+     *
+     * @return A list of key/value pairs that were previously passed to the context.
+     */
+    public List<CapturedForward<KForward, VForward>> forwarded() {
+        return new LinkedList<>(capturedForwards);
+    }
+
+    /**
+     * Get all the forwarded data this context has observed for a specific child by name.
+     * The returned list will not be affected by subsequent interactions with the context.
+     * The data in the list is in the same order as the calls to {@code forward(...)}.
+     *
+     * @param childName The child name to retrieve forwards for
+     * @return A list of key/value pairs that were previously passed to the context.
+     */
+    @SuppressWarnings("unused")
+    public List<CapturedForward<KForward, VForward>> forwarded(final String childName) {
+        final LinkedList<CapturedForward<KForward, VForward>> result = new LinkedList<>();
+        for (final CapturedForward<KForward, VForward> capture : capturedForwards) {
+            if (capture.childName() == null || capture.childName().equals(childName)) {
+                result.add(capture);
+            }
+        }
+        return result;
+    }
+
+    /**
+     * Clear the captured forwarded data.
+     */
+    @SuppressWarnings("unused")
+    public void resetForwards() {
+        capturedForwards.clear();
+    }
+
+    @Override
+    public void commit() {
+        committed = true;
+    }
+
+    /**
+     * Whether {@link ProcessorContext#commit()} has been called in this context.
+     *
+     * @return {@code true} iff {@link ProcessorContext#commit()} has been called in this context since construction or reset.
+     */
+    public boolean committed() {
+        return committed;
+    }
+
+    /**
+     * Reset the commit capture to {@code false} (whether or not it was previously {@code true}).
+     */
+    @SuppressWarnings("unused")
+    public void resetCommit() {
+        committed = false;
+    }
+
+    @Override
+    public RecordCollector recordCollector() {
+        // This interface is assumed by state stores that add change-logging.
+        // Rather than risk a mysterious ClassCastException during unit tests, throw an explanatory exception.
+
+        throw new UnsupportedOperationException(
+            "MockProcessorContext does not provide record collection. " +
+                "For processor unit tests, use an in-memory state store with change-logging disabled. " +
+                "Alternatively, use the TopologyTestDriver for testing processor/store/topology integration."
+        );
+    }
+
+    private static long getTimestamp(final To to) {
+        final long timestamp;
+        try {
+            final Field field = To.class.getDeclaredField("timestamp");
+            field.setAccessible(true);
+            timestamp = (long) field.get(to);
+        } catch (final IllegalAccessException | NoSuchFieldException e) {
+            throw new RuntimeException(e);
+        }
+        return timestamp;
+    }
+}
diff --git a/streams/test-utils/src/test/java/org/apache/kafka/streams/MockApiProcessorContextTest.java b/streams/test-utils/src/test/java/org/apache/kafka/streams/MockApiProcessorContextTest.java
new file mode 100644
index 0000000..6e9c5a6
--- /dev/null
+++ b/streams/test-utils/src/test/java/org/apache/kafka/streams/MockApiProcessorContextTest.java
@@ -0,0 +1,405 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams;
+
+import org.apache.kafka.common.serialization.Serdes;
+import org.apache.kafka.streams.processor.api.MockProcessorContext;
+import org.apache.kafka.streams.processor.api.MockProcessorContext.CapturedForward;
+import org.apache.kafka.streams.processor.PunctuationType;
+import org.apache.kafka.streams.processor.Punctuator;
+import org.apache.kafka.streams.processor.TaskId;
+import org.apache.kafka.streams.processor.To;
+import org.apache.kafka.streams.processor.api.Processor;
+import org.apache.kafka.streams.processor.api.ProcessorContext;
+import org.apache.kafka.streams.processor.internals.ProcessorContextReverseAdapter;
+import org.apache.kafka.streams.state.KeyValueStore;
+import org.apache.kafka.streams.state.StoreBuilder;
+import org.apache.kafka.streams.state.Stores;
+import org.junit.Test;
+
+import java.io.File;
+import java.time.Duration;
+import java.util.Iterator;
+import java.util.Properties;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+public class MockApiProcessorContextTest {
+    @Test
+    public void shouldCaptureOutputRecords() {
+        final Processor<String, Long, String, Long> processor = new Processor<String, Long, String, Long>() {
+            private ProcessorContext<String, Long> context;
+
+            @Override
+            public void init(final ProcessorContext<String, Long> context) {
+                this.context = context;
+            }
+
+            @Override
+            public void process(final String key, final Long value) {
+                context.forward(key + value, key.length() + value);
+            }
+        };
+
+        final MockProcessorContext<String, Long> context = new MockProcessorContext<>();
+        processor.init(context);
+
+        processor.process("foo", 5L);
+        processor.process("barbaz", 50L);
+
+        final Iterator<CapturedForward<String, Long>> forwarded = context.forwarded().iterator();
+        assertEquals(new KeyValue<>("foo5", 8L), forwarded.next().keyValue());
+        assertEquals(new KeyValue<>("barbaz50", 56L), forwarded.next().keyValue());
+        assertFalse(forwarded.hasNext());
+
+        context.resetForwards();
+
+        assertEquals(0, context.forwarded().size());
+    }
+
+    @Test
+    public void shouldCaptureOutputRecordsUsingTo() {
+        final Processor<String, Long, String, Long> processor = new Processor<String, Long, String, Long>() {
+            private ProcessorContext<String, Long> context;
+
+            @Override
+            public void init(final ProcessorContext<String, Long> context) {
+                this.context = context;
+            }
+
+            @Override
+            public void process(final String key, final Long value) {
+                context.forward(key + value, key.length() + value, To.all());
+            }
+        };
+
+        final MockProcessorContext<String, Long> context = new MockProcessorContext<>();
+
+        processor.init(context);
+
+        processor.process("foo", 5L);
+        processor.process("barbaz", 50L);
+
+        final Iterator<CapturedForward<String, Long>> forwarded = context.forwarded().iterator();
+        assertEquals(new KeyValue<>("foo5", 8L), forwarded.next().keyValue());
+        assertEquals(new KeyValue<>("barbaz50", 56L), forwarded.next().keyValue());
+        assertFalse(forwarded.hasNext());
+
+        context.resetForwards();
+
+        assertEquals(0, context.forwarded().size());
+    }
+
+    @Test
+    public void shouldCaptureRecordsOutputToChildByName() {
+        final Processor<String, Long, String, Long> processor = new Processor<String, Long, String, Long>() {
+            private int count = 0;
+            private ProcessorContext<String, Long> context;
+
+            @Override
+            public void init(final ProcessorContext<String, Long> context) {
+                this.context = context;
+            }
+
+            @Override
+            public void process(final String key, final Long value) {
+                if (count == 0) {
+                    context.forward("start", -1L, To.all()); // broadcast
+                }
+                final To toChild = count % 2 == 0 ? To.child("george") : To.child("pete");
+                context.forward(key + value, key.length() + value, toChild);
+                count++;
+            }
+        };
+
+        final MockProcessorContext<String, Long> context = new MockProcessorContext<>();
+
+        processor.init(context);
+
+        processor.process("foo", 5L);
+        processor.process("barbaz", 50L);
+
+        {
+            final Iterator<CapturedForward<String, Long>> forwarded = context.forwarded().iterator();
+
+            final CapturedForward forward1 = forwarded.next();
+            assertEquals(new KeyValue<>("start", -1L), forward1.keyValue());
+            assertNull(forward1.childName());
+
+            final CapturedForward forward2 = forwarded.next();
+            assertEquals(new KeyValue<>("foo5", 8L), forward2.keyValue());
+            assertEquals("george", forward2.childName());
+
+            final CapturedForward forward3 = forwarded.next();
+            assertEquals(new KeyValue<>("barbaz50", 56L), forward3.keyValue());
+            assertEquals("pete", forward3.childName());
+
+            assertFalse(forwarded.hasNext());
+        }
+
+        {
+            final Iterator<CapturedForward<String, Long>> forwarded = context.forwarded("george").iterator();
+            assertEquals(new KeyValue<>("start", -1L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("foo5", 8L), forwarded.next().keyValue());
+            assertFalse(forwarded.hasNext());
+        }
+
+        {
+            final Iterator<CapturedForward<String, Long>> forwarded = context.forwarded("pete").iterator();
+            assertEquals(new KeyValue<>("start", -1L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("barbaz50", 56L), forwarded.next().keyValue());
+            assertFalse(forwarded.hasNext());
+        }
+
+        {
+            final Iterator<CapturedForward<String, Long>> forwarded = context.forwarded("steve").iterator();
+            assertEquals(new KeyValue<>("start", -1L), forwarded.next().keyValue());
+            assertFalse(forwarded.hasNext());
+        }
+    }
+
+    @Test
+    public void shouldCaptureCommitsAndAllowReset() {
+        final Processor<String, Long, Void, Void> processor = new Processor<String, Long, Void, Void>() {
+            private int count = 0;
+            private ProcessorContext<Void, Void> context;
+
+            @Override
+            public void init(final ProcessorContext<Void, Void> context) {
+                this.context = context;
+            }
+
+            @Override
+            public void process(final String key, final Long value) {
+                if (++count > 2) {
+                    context.commit();
+                }
+            }
+        };
+
+        final MockProcessorContext<Void, Void> context = new MockProcessorContext<>();
+
+        processor.init(context);
+
+        processor.process("foo", 5L);
+        processor.process("barbaz", 50L);
+
+        assertFalse(context.committed());
+
+        processor.process("foobar", 500L);
+
+        assertTrue(context.committed());
+
+        context.resetCommit();
+
+        assertFalse(context.committed());
+    }
+
+    @SuppressWarnings("unchecked")
+    @Test
+    public void shouldStoreAndReturnStateStores() {
+        final Processor<String, Long, Void, Void> processor = new Processor<String, Long, Void, Void>() {
+            private ProcessorContext<Void, Void> context;
+
+            @Override
+            public void init(final ProcessorContext<Void, Void> context) {
+                this.context = context;
+            }
+
+            @Override
+            public void process(final String key, final Long value) {
+                final KeyValueStore<String, Long> stateStore = context.getStateStore("my-state");
+                stateStore.put(key, (stateStore.get(key) == null ? 0 : stateStore.get(key)) + value);
+                stateStore.put("all", (stateStore.get("all") == null ? 0 : stateStore.get("all")) + value);
+            }
+        };
+
+        final MockProcessorContext<Void, Void> context = new MockProcessorContext<>();
+
+        final StoreBuilder<KeyValueStore<String, Long>> storeBuilder = Stores.keyValueStoreBuilder(
+                Stores.inMemoryKeyValueStore("my-state"),
+                Serdes.String(),
+                Serdes.Long()).withLoggingDisabled();
+
+        final KeyValueStore<String, Long> store = storeBuilder.build();
+
+        store.init(ProcessorContextReverseAdapter.adapt(context, new ProcessorContextReverseAdapter.DeprecatedForwarder() {
+            @Override
+            public <K, V> void forward(final K key, final V value, final int childIndex) {
+                throw new UnsupportedOperationException();
+            }
+        }), store);
+
+        processor.init(context);
+
+        processor.process("foo", 5L);
+        processor.process("bar", 50L);
+
+        assertEquals(5L, (long) store.get("foo"));
+        assertEquals(50L, (long) store.get("bar"));
+        assertEquals(55L, (long) store.get("all"));
+    }
+
+    @Test
+    public void shouldCaptureApplicationAndRecordMetadata() {
+        final Properties config = new Properties();
+        config.put(StreamsConfig.APPLICATION_ID_CONFIG, "testMetadata");
+        config.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "");
+
+        final Processor<String, Object, String, Object> processor = new Processor<String, Object, String, Object>() {
+            private ProcessorContext<String, Object> context;
+
+            @Override
+            public void init(final ProcessorContext<String, Object> context) {
+                this.context = context;
+            }
+
+            @Override
+            public void process(final String key, final Object value) {
+                context.forward("appId", context.applicationId());
+                context.forward("taskId", context.taskId());
+
+                context.forward("topic", context.topic());
+                context.forward("partition", context.partition());
+                context.forward("offset", context.offset());
+                context.forward("timestamp", context.timestamp());
+
+                context.forward("key", key);
+                context.forward("value", value);
+            }
+        };
+
+        final MockProcessorContext<String, Object> context = new MockProcessorContext<>(config);
+        processor.init(context);
+
+        try {
+            processor.process("foo", 5L);
+            fail("Should have thrown an exception.");
+        } catch (final IllegalStateException expected) {
+            // expected, since the record metadata isn't initialized
+        }
+
+        context.resetForwards();
+        context.setRecordMetadata("t1", 0, 0L, null, 0L);
+
+        {
+            processor.process("foo", 5L);
+            final Iterator<CapturedForward<String, Object>> forwarded = context.forwarded().iterator();
+            assertEquals(new KeyValue<>("appId", "testMetadata"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("taskId", new TaskId(0, 0)), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("topic", "t1"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("partition", 0), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("offset", 0L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("timestamp", 0L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("key", "foo"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("value", 5L), forwarded.next().keyValue());
+        }
+
+        context.resetForwards();
+
+        // record metadata should be "sticky"
+        context.setOffset(1L);
+        context.setTimestamp(10L);
+
+        {
+            processor.process("bar", 50L);
+            final Iterator<CapturedForward<String, Object>> forwarded = context.forwarded().iterator();
+            assertEquals(new KeyValue<>("appId", "testMetadata"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("taskId", new TaskId(0, 0)), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("topic", "t1"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("partition", 0), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("offset", 1L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("timestamp", 10L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("key", "bar"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("value", 50L), forwarded.next().keyValue());
+        }
+
+        context.resetForwards();
+        // record metadata should be "sticky"
+        context.setTopic("t2");
+        context.setPartition(30);
+
+        {
+            processor.process("baz", 500L);
+            final Iterator<CapturedForward<String, Object>> forwarded = context.forwarded().iterator();
+            assertEquals(new KeyValue<>("appId", "testMetadata"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("taskId", new TaskId(0, 0)), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("topic", "t2"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("partition", 30), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("offset", 1L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("timestamp", 10L), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("key", "baz"), forwarded.next().keyValue());
+            assertEquals(new KeyValue<>("value", 500L), forwarded.next().keyValue());
+        }
+    }
+
+    @Test
+    public void shouldCapturePunctuator() {
+        final Processor<String, Long, Void, Void> processor = new Processor<String, Long, Void, Void>() {
+            @Override
+            public void init(final ProcessorContext<Void, Void> context) {
+                context.schedule(
+                    Duration.ofSeconds(1L),
+                    PunctuationType.WALL_CLOCK_TIME,
+                    timestamp -> context.commit()
+                );
+            }
+
+            @Override
+            public void process(final String key, final Long value) {
+            }
+        };
+
+        final MockProcessorContext<Void, Void> context = new MockProcessorContext<>();
+
+        processor.init(context);
+
+        final MockProcessorContext.CapturedPunctuator capturedPunctuator = context.scheduledPunctuators().get(0);
+        assertEquals(1000L, capturedPunctuator.getIntervalMs());
+        assertEquals(PunctuationType.WALL_CLOCK_TIME, capturedPunctuator.getType());
+        assertFalse(capturedPunctuator.cancelled());
+
+        final Punctuator punctuator = capturedPunctuator.getPunctuator();
+        assertFalse(context.committed());
+        punctuator.punctuate(1234L);
+        assertTrue(context.committed());
+    }
+
+    @Test
+    public void fullConstructorShouldSetAllExpectedAttributes() {
+        final Properties config = new Properties();
+        config.put(StreamsConfig.APPLICATION_ID_CONFIG, "testFullConstructor");
+        config.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "");
+        config.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
+        config.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.Long().getClass());
+
+        final File dummyFile = new File("");
+        final MockProcessorContext<Void, Void> context = new MockProcessorContext<>(config, new TaskId(1, 1), dummyFile);
+
+        assertEquals("testFullConstructor", context.applicationId());
+        assertEquals(new TaskId(1, 1), context.taskId());
+        assertEquals("testFullConstructor", context.appConfigs().get(StreamsConfig.APPLICATION_ID_CONFIG));
+        assertEquals("testFullConstructor", context.appConfigsWithPrefix("application.").get("id"));
+        assertEquals(Serdes.String().getClass(), context.keySerde().getClass());
+        assertEquals(Serdes.Long().getClass(), context.valueSerde().getClass());
+        assertEquals(dummyFile, context.stateDir());
+    }
+}