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Posted to issues@flink.apache.org by "echauchot (via GitHub)" <gi...@apache.org> on 2023/04/14 14:29:34 UTC
[GitHub] [flink-web] echauchot opened a new pull request, #643: Add blog article: Howto test a batch source with the new Source framework
echauchot opened a new pull request, #643:
URL: https://github.com/apache/flink-web/pull/643
Last article of the series about testing the created batch source in the previous article.
R:@zentol. Feel free to delegate as you have already the previous 2 articles to review.
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192029322
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
Review Comment:
done
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192157171
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
Review Comment:
ok fair enough, in that case I'll also remove "runtime" from the "Flink runtime environment" title for coherence.
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192004345
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
Review Comment:
:+1:
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192083594
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
Review Comment:
done
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192021200
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
Review Comment:
:+1:
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
Review Comment:
done
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[GitHub] [flink-web] echauchot commented on pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on PR #643:
URL: https://github.com/apache/flink-web/pull/643#issuecomment-1545544022
> > I took a quick look over it. I feel especially for the IT case it would be nice to first provide an overview over the differnet parts that make up a test "There's a test framework; We need a backend the source can read from, a test context for Flinks testing framework to interact with the backend, ..." and then drill down into the details as you already did.
> > Right now it's very "I have to do this and this and this" but you don't really know where you're heading.
>
> Totally agree, I'll do something similar to what I did on the source creation blog: an architecture paragraph
done
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[GitHub] [flink-web] zentol commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "zentol (via GitHub)" <gi...@apache.org>.
zentol commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1189562453
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
Review Comment:
```suggestion
we create an object, serialize it using the serializer and then deserialize it using the same
```
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
Review Comment:
```suggestion
[Example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
```
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
Review Comment:
```suggestion
for Split and SplitEnumeratorState. We should now test them in unit tests. To test serde
```
using "usual" in a howto seems odd
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
+`
+
+BackendTestEnvironment
+implements [TestResource](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html)
+. This environment is scoped to the test suite so it is where we setup the backend runtime and
+shared resources (session, tablespace, etc...) by
+implementing [startup()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#startUp--)
+and [tearDown()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#tearDown--)
+methods. For
+that we advice the use of [testContainers](https://www.testcontainers.org/) that relies on docker
+images to provide a real backend
+instance (not a mock) that is representative for integration tests. Several backends are supported
+out of the box by testContainers. We need to configure test containers that way:
+
+* Redirect container output (error and standard output) to Flink logs
+* Set the different timeouts to cope with CI server load
+* Set retrial mechanisms for connection, initialization requests etc... for the same reason
+
+### Checkpointing semantics
+
+In big data execution engines, there are 2 levels of guaranty regarding source and sinks:
Review Comment:
```suggestion
In big data execution engines, there are 2 levels of guarantee regarding source and sinks:
```
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
Review Comment:
Maybe some high-level intro line what this is about could be helpful.
Something like "To test the connector we need a backend to run the connector against. Something something need to implement something to integrate this into junit5; maybe provided by library."
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
+`
+
+BackendTestEnvironment
+implements [TestResource](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html)
+. This environment is scoped to the test suite so it is where we setup the backend runtime and
+shared resources (session, tablespace, etc...) by
+implementing [startup()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#startUp--)
+and [tearDown()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#tearDown--)
+methods. For
+that we advice the use of [testContainers](https://www.testcontainers.org/) that relies on docker
+images to provide a real backend
+instance (not a mock) that is representative for integration tests. Several backends are supported
+out of the box by testContainers. We need to configure test containers that way:
+
+* Redirect container output (error and standard output) to Flink logs
+* Set the different timeouts to cope with CI server load
+* Set retrial mechanisms for connection, initialization requests etc... for the same reason
+
+### Checkpointing semantics
+
+In big data execution engines, there are 2 levels of guaranty regarding source and sinks:
+
+* At least once: upon failure and recovery, some records may be reflected multiple times but none
+ will
+ be lost
+* Exactly once: upon failure and recovery, every record will be reflected exactly once
+ By the following code we verify that the source supports exactly once semantics:
+
+`@TestSemantics
+CheckpointingMode[] semantics = new CheckpointingMode[] {CheckpointingMode.EXACTLY_ONCE};
+`
+
+That being said, we could encounter a problem while running the tests : the default assertions in
+the Flink source test framework assume that the data is read in the same order it was written. This
+is untrue for most big data backends where ordering is usually not deterministic. To support
+unordered checks and still use all the framework provided tests, we need to override
+[SourceTestSuiteBase#checkResultWithSemantic](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html#checkResultWithSemantic-org.apache.flink.util.CloseableIterator-java.util.List-org.apache.flink.streaming.api.CheckpointingMode-java.lang.Integer-)
+in out ITCase:
+
+`@Override
+protected void checkResultWithSemantic(
+CloseableIterator<Pojo> resultIterator,
+List<List<Pojo>> testData,
+CheckpointingMode semantic,
+Integer limit) {
+if (limit != null) {
+Runnable runnable =
+() ->
+CollectIteratorAssertions.assertUnordered(resultIterator)
+.withNumRecordsLimit(limit)
+.matchesRecordsFromSource(testData, semantic);
+
+ assertThat(runAsync(runnable)).succeedsWithin(DEFAULT_COLLECT_DATA_TIMEOUT);
+ } else {
+ CollectIteratorAssertions.assertUnordered(resultIterator)
+ .matchesRecordsFromSource(testData, semantic);
+ }
+
+}`
+
+This is simply a copy-paste of the parent method where _CollectIteratorAssertions.assertOrdered()_
+is
+replaced by _CollectIteratorAssertions.assertUnordered()_.
+
+### Test context
+
+[example Cassandra TestContext](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestContext.java)
+
+The test context is scoped to the test case. So it is where we do things like creating test table,
+creating the source or writing test data.
Review Comment:
```suggestion
The test context provides Flink with means to interact with the backend, like inserting test data/tables or constructing sources/sink.
```
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
Review Comment:
```suggestion
### Backend environment
```
It is never referenced as "backend **runtime** environment" in subsequent sections
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
Review Comment:
```suggestion
MyBackendTestEnvironment backendTestEnvironment = new MyBackendTestEnvironment();
```
Maybe makes it a bit clearer that this is something implemented by the user.
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
+`
+
+BackendTestEnvironment
+implements [TestResource](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html)
+. This environment is scoped to the test suite so it is where we setup the backend runtime and
+shared resources (session, tablespace, etc...) by
+implementing [startup()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#startUp--)
+and [tearDown()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#tearDown--)
+methods. For
+that we advice the use of [testContainers](https://www.testcontainers.org/) that relies on docker
+images to provide a real backend
+instance (not a mock) that is representative for integration tests. Several backends are supported
+out of the box by testContainers. We need to configure test containers that way:
+
+* Redirect container output (error and standard output) to Flink logs
+* Set the different timeouts to cope with CI server load
+* Set retrial mechanisms for connection, initialization requests etc... for the same reason
+
+### Checkpointing semantics
+
+In big data execution engines, there are 2 levels of guaranty regarding source and sinks:
+
+* At least once: upon failure and recovery, some records may be reflected multiple times but none
+ will
+ be lost
+* Exactly once: upon failure and recovery, every record will be reflected exactly once
+ By the following code we verify that the source supports exactly once semantics:
Review Comment:
```suggestion
By the following code we verify that the source supports exactly once semantics:
```
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
Review Comment:
```suggestion
we create an *ITCase named class that
```
The name only really matters if the test is added to Flink. I think we shouldn't assume that because users might have their own sources they want to test that won't be contributed to Flink.
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
+`
+
+BackendTestEnvironment
+implements [TestResource](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html)
+. This environment is scoped to the test suite so it is where we setup the backend runtime and
+shared resources (session, tablespace, etc...) by
+implementing [startup()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#startUp--)
+and [tearDown()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#tearDown--)
+methods. For
+that we advice the use of [testContainers](https://www.testcontainers.org/) that relies on docker
+images to provide a real backend
+instance (not a mock) that is representative for integration tests. Several backends are supported
+out of the box by testContainers. We need to configure test containers that way:
+
+* Redirect container output (error and standard output) to Flink logs
+* Set the different timeouts to cope with CI server load
+* Set retrial mechanisms for connection, initialization requests etc... for the same reason
+
+### Checkpointing semantics
+
+In big data execution engines, there are 2 levels of guaranty regarding source and sinks:
+
+* At least once: upon failure and recovery, some records may be reflected multiple times but none
+ will
+ be lost
+* Exactly once: upon failure and recovery, every record will be reflected exactly once
+ By the following code we verify that the source supports exactly once semantics:
+
+`@TestSemantics
+CheckpointingMode[] semantics = new CheckpointingMode[] {CheckpointingMode.EXACTLY_ONCE};
+`
+
+That being said, we could encounter a problem while running the tests : the default assertions in
+the Flink source test framework assume that the data is read in the same order it was written. This
+is untrue for most big data backends where ordering is usually not deterministic. To support
+unordered checks and still use all the framework provided tests, we need to override
+[SourceTestSuiteBase#checkResultWithSemantic](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html#checkResultWithSemantic-org.apache.flink.util.CloseableIterator-java.util.List-org.apache.flink.streaming.api.CheckpointingMode-java.lang.Integer-)
+in out ITCase:
+
+`@Override
+protected void checkResultWithSemantic(
+CloseableIterator<Pojo> resultIterator,
+List<List<Pojo>> testData,
+CheckpointingMode semantic,
+Integer limit) {
+if (limit != null) {
+Runnable runnable =
+() ->
+CollectIteratorAssertions.assertUnordered(resultIterator)
+.withNumRecordsLimit(limit)
+.matchesRecordsFromSource(testData, semantic);
+
+ assertThat(runAsync(runnable)).succeedsWithin(DEFAULT_COLLECT_DATA_TIMEOUT);
+ } else {
+ CollectIteratorAssertions.assertUnordered(resultIterator)
+ .matchesRecordsFromSource(testData, semantic);
+ }
+
+}`
+
+This is simply a copy-paste of the parent method where _CollectIteratorAssertions.assertOrdered()_
Review Comment:
```suggestion
This is a copy-paste of the parent method where _CollectIteratorAssertions.assertOrdered()_
```
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192167315
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
+`
+
+BackendTestEnvironment
+implements [TestResource](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html)
+. This environment is scoped to the test suite so it is where we setup the backend runtime and
+shared resources (session, tablespace, etc...) by
+implementing [startup()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#startUp--)
+and [tearDown()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#tearDown--)
+methods. For
+that we advice the use of [testContainers](https://www.testcontainers.org/) that relies on docker
+images to provide a real backend
+instance (not a mock) that is representative for integration tests. Several backends are supported
+out of the box by testContainers. We need to configure test containers that way:
+
+* Redirect container output (error and standard output) to Flink logs
+* Set the different timeouts to cope with CI server load
+* Set retrial mechanisms for connection, initialization requests etc... for the same reason
+
+### Checkpointing semantics
+
+In big data execution engines, there are 2 levels of guaranty regarding source and sinks:
+
+* At least once: upon failure and recovery, some records may be reflected multiple times but none
+ will
+ be lost
+* Exactly once: upon failure and recovery, every record will be reflected exactly once
+ By the following code we verify that the source supports exactly once semantics:
+
+`@TestSemantics
+CheckpointingMode[] semantics = new CheckpointingMode[] {CheckpointingMode.EXACTLY_ONCE};
+`
+
+That being said, we could encounter a problem while running the tests : the default assertions in
+the Flink source test framework assume that the data is read in the same order it was written. This
+is untrue for most big data backends where ordering is usually not deterministic. To support
+unordered checks and still use all the framework provided tests, we need to override
+[SourceTestSuiteBase#checkResultWithSemantic](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html#checkResultWithSemantic-org.apache.flink.util.CloseableIterator-java.util.List-org.apache.flink.streaming.api.CheckpointingMode-java.lang.Integer-)
+in out ITCase:
+
+`@Override
+protected void checkResultWithSemantic(
+CloseableIterator<Pojo> resultIterator,
+List<List<Pojo>> testData,
+CheckpointingMode semantic,
+Integer limit) {
+if (limit != null) {
+Runnable runnable =
+() ->
+CollectIteratorAssertions.assertUnordered(resultIterator)
+.withNumRecordsLimit(limit)
+.matchesRecordsFromSource(testData, semantic);
+
+ assertThat(runAsync(runnable)).succeedsWithin(DEFAULT_COLLECT_DATA_TIMEOUT);
+ } else {
+ CollectIteratorAssertions.assertUnordered(resultIterator)
+ .matchesRecordsFromSource(testData, semantic);
+ }
+
+}`
+
+This is simply a copy-paste of the parent method where _CollectIteratorAssertions.assertOrdered()_
+is
+replaced by _CollectIteratorAssertions.assertUnordered()_.
+
+### Test context
+
+[example Cassandra TestContext](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestContext.java)
+
+The test context is scoped to the test case. So it is where we do things like creating test table,
+creating the source or writing test data.
Review Comment:
Agree with the rephrasing but I'd like also to keep the important notion of test case scope of the TestContext (compared to test suite scope of the backend environment)
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[GitHub] [flink-web] echauchot commented on pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on PR #643:
URL: https://github.com/apache/flink-web/pull/643#issuecomment-1545283430
> I took a quick look over it. I feel especially for the IT case it would be nice to first provide an overview over the differnet parts that make up a test "There's a test framework; We need a backend the source can read from, a test context for Flinks testing framework to interact with the backend, ..." and then drill down into the details as you already did.
>
> Right now it's very "I have to do this and this and this" but you don't really know where you're heading.
Totally agree, thanks for the suggestion
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192157171
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
Review Comment:
ok fair enough, in that case I'll also remove "runtime" from "Flink runtime environment" title for coherence.
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192162301
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
Review Comment:
done
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192171185
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
+`
+
+BackendTestEnvironment
+implements [TestResource](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html)
+. This environment is scoped to the test suite so it is where we setup the backend runtime and
+shared resources (session, tablespace, etc...) by
+implementing [startup()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#startUp--)
+and [tearDown()](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/TestResource.html#tearDown--)
+methods. For
+that we advice the use of [testContainers](https://www.testcontainers.org/) that relies on docker
+images to provide a real backend
+instance (not a mock) that is representative for integration tests. Several backends are supported
+out of the box by testContainers. We need to configure test containers that way:
+
+* Redirect container output (error and standard output) to Flink logs
+* Set the different timeouts to cope with CI server load
+* Set retrial mechanisms for connection, initialization requests etc... for the same reason
+
+### Checkpointing semantics
+
+In big data execution engines, there are 2 levels of guaranty regarding source and sinks:
+
+* At least once: upon failure and recovery, some records may be reflected multiple times but none
+ will
+ be lost
+* Exactly once: upon failure and recovery, every record will be reflected exactly once
+ By the following code we verify that the source supports exactly once semantics:
+
+`@TestSemantics
+CheckpointingMode[] semantics = new CheckpointingMode[] {CheckpointingMode.EXACTLY_ONCE};
+`
+
+That being said, we could encounter a problem while running the tests : the default assertions in
+the Flink source test framework assume that the data is read in the same order it was written. This
+is untrue for most big data backends where ordering is usually not deterministic. To support
+unordered checks and still use all the framework provided tests, we need to override
+[SourceTestSuiteBase#checkResultWithSemantic](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html#checkResultWithSemantic-org.apache.flink.util.CloseableIterator-java.util.List-org.apache.flink.streaming.api.CheckpointingMode-java.lang.Integer-)
+in out ITCase:
+
+`@Override
+protected void checkResultWithSemantic(
+CloseableIterator<Pojo> resultIterator,
+List<List<Pojo>> testData,
+CheckpointingMode semantic,
+Integer limit) {
+if (limit != null) {
+Runnable runnable =
+() ->
+CollectIteratorAssertions.assertUnordered(resultIterator)
+.withNumRecordsLimit(limit)
+.matchesRecordsFromSource(testData, semantic);
+
+ assertThat(runAsync(runnable)).succeedsWithin(DEFAULT_COLLECT_DATA_TIMEOUT);
+ } else {
+ CollectIteratorAssertions.assertUnordered(resultIterator)
+ .matchesRecordsFromSource(testData, semantic);
+ }
+
+}`
+
+This is simply a copy-paste of the parent method where _CollectIteratorAssertions.assertOrdered()_
+is
+replaced by _CollectIteratorAssertions.assertUnordered()_.
+
+### Test context
+
+[example Cassandra TestContext](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestContext.java)
+
+The test context is scoped to the test case. So it is where we do things like creating test table,
+creating the source or writing test data.
Review Comment:
done
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192030443
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
+we just create an object, serialize it using the serializer and then deserialize it using the same
+serializer and finally assert on the equality of the two objects. Thus, hascode() and equals() need
+to be implemented for the serialized objects.
+
+### Other unit tests
+
+Of course, we also need to unit test low level processing such as query building for example or any
+processing that does not require a running backend.
+
+## Integration testing the source
+
+[example Cassandra SourceITCase
+](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraSourceITCase.java)
+
+For tests that require a running backend, Flink provides a JUnit5 source test framework. To use it
+we create an *ITCase named class that
+extends [SourceTestSuiteBase](https://nightlies.apache.org/flink/flink-docs-master/api/java/org/apache/flink/connector/testframe/testsuites/SourceTestSuiteBase.html)
+. This test suite provides all
+the necessary tests already (single split, multiple splits, idle reader, etc...). It is targeted for
+batch and streaming sources, so for our batch source case here, the tests below need to be disabled
+as they are targeted for streaming sources. They can be disabled by overriding them in the ITCase
+and annotating them with @Disabled:
+
+* testSourceMetrics
+* testSavepoint
+* testScaleUp
+* testScaleDown
+* testTaskManagerFailure
+
+Of course we can add our own integration tests cases for example tests on limits, tests on low level
+splitting or any test that requires a running backend. But for most cases we only need to provide
+Flink test environment classes to configure the ITCase:
+
+### Flink runtime environment
+
+We add this annotated field to our ITCase and we're done
+
+`@TestEnv
+MiniClusterTestEnvironment flinkTestEnvironment = new MiniClusterTestEnvironment();
+`
+
+### Backend runtime environment
+
+[example Cassandra TestEnvironment](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/test/java/org/apache/flink/connector/cassandra/source/CassandraTestEnvironment.java)
+
+We add this annotated field to our ITCase
+
+`@TestExternalSystem
+BackendTestEnvironment backendTestEnvironment = new BackendTestEnvironment();
Review Comment:
agree
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[GitHub] [flink-web] echauchot commented on pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on PR #643:
URL: https://github.com/apache/flink-web/pull/643#issuecomment-1534918324
@MartijnVisser @zentol did almost all my last reviews. Would you have time to review this small article as you know the source framework ?
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[GitHub] [flink-web] echauchot merged pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot merged PR #643:
URL: https://github.com/apache/flink-web/pull/643
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[GitHub] [flink-web] echauchot commented on a diff in pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on code in PR #643:
URL: https://github.com/apache/flink-web/pull/643#discussion_r1192003814
##########
docs/content/posts/howto-test-batch-source.md:
##########
@@ -0,0 +1,202 @@
+---
+title: "Howto test a batch source with the new Source framework"
+date: "2023-04-14T08:00:00.000Z"
+authors:
+- echauchot:
+ name: "Etienne Chauchot"
+ twitter: "echauchot"
+
+---
+
+## Introduction
+
+The Flink community has
+designed [a new Source framework](https://nightlies.apache.org/flink/flink-docs-release-1.16/docs/dev/datastream/sources/)
+based
+on [FLIP-27](https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface)
+lately. This article is the
+continuation of
+the [howto create a batch source with the new Source framework article](https://flink.apache.org/2023/04/14/howto-create-batch-source/)
+. Now it is
+time to test the created source ! As the previous article, this one was built while implementing the
+[Flink batch source](https://github.com/apache/flink-connector-cassandra/commit/72e3bef1fb9ee6042955b5e9871a9f70a8837cca)
+for [Cassandra](https://cassandra.apache.org/_/index.html).
+
+## Unit testing the source
+
+### Testing the serializers
+
+[example Cassandra SplitSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/split/CassandraSplitSerializer.java)
+and [SplitEnumeratorStateSerializer](https://github.com/apache/flink-connector-cassandra/blob/d92dc8d891098a9ca6a7de6062b4630079beaaef/flink-connector-cassandra/src/main/java/org/apache/flink/connector/cassandra/source/enumerator/CassandraEnumeratorStateSerializer.java)
+
+In the previous article, we
+created [serializers](https://flink.apache.org/2023/04/14/howto-create-batch-source/#serializers)
+for Split and SplitEnumeratorState. We should now test them in unit tests. As usual, to test serde
Review Comment:
agree
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[GitHub] [flink-web] echauchot commented on pull request #643: Add blog article: Howto test a batch source with the new Source framework
Posted by "echauchot (via GitHub)" <gi...@apache.org>.
echauchot commented on PR #643:
URL: https://github.com/apache/flink-web/pull/643#issuecomment-1545554335
@zentol Thanks for your review (once again). I addressed all your comments PTAL
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