[FLINK-39124][test] Migrate remaining flink-tests to JUnit 5 by mateczagany · Pull Request #27669 · apache/flink

mateczagany · 2026-02-25T07:49:14Z

What is the purpose of the change

Migrate some of the tests in module flink-tests from JUnit4 to JUnit5.

Brief change log

Migrate all test cases to use JUnit5.
Update all assertions to assertThat()
Limit scope for test classes where possible
Restrict visibility of fields where possible
Remove @SuppressWarnings where it was unnecessary

Verifying this change

I ran each updated tests one by one after migrating them
CI should pass

Does this pull request potentially affect one of the following parts:

Dependencies (does it add or upgrade a dependency): no
The public API, i.e., is any changed class annotated with @Public(Evolving): no
The serializers: no
The runtime per-record code paths (performance sensitive): no
Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
The S3 file system connector: no

Documentation

Does this pull request introduce a new feature? no
If yes, how is the feature documented? not applicable

flinkbot · 2026-02-25T07:57:56Z

CI report:

bed5fc4 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

@flinkbot run azure re-run the last Azure build

flink-tests/src/test/java/org/apache/flink/test/accumulators/AccumulatorErrorITCase.java

flink-tests/src/test/java/org/apache/flink/test/accumulators/AccumulatorITCase.java

flink-tests/src/test/java/org/apache/flink/test/example/client/LocalExecutorITCase.java

flink-tests/src/test/java/org/apache/flink/test/accumulators/AccumulatorITCase.java

snuyanzin · 2026-03-02T20:14:50Z

flink-tests/src/test/java/org/apache/flink/test/misc/MiscellaneousIssuesITCase.java

@@ -84,12 +84,12 @@ public String map(String value) throws Exception {
            env.execute();
            fail("this should fail due to null values.");
        } catch (JobExecutionException e) {
-            assertTrue(findThrowable(e, NullPointerException.class).isPresent());
+            assertThat(findThrowable(e, NullPointerException.class)).isPresent();
        }
    }


can we replace it with something like

assertThatThrownBy(env::execute) .isInstanceOf(JobExecutionException.class) .hasRootCauseInstanceOf(NullPointerException.class);

same for other try catches in this PR

Thank you, I've updated this and each other instance I found in the updated files. I also tried to look for other cases where improvement could be made.

mateczagany · 2026-03-04T13:19:10Z

flink-tests/src/test/java/org/apache/flink/test/misc/CustomSerializationITCase.java

-                                                    .contains("broken serialization."))
-                            .isPresent());
-        }
+    @Disabled("TODO: This needs to be investigated why no exception is thrown.")


During rewriting this test, I found that these test cases don't even check if the exception is thrown. Only the 2nd test passes, so I've disabled the others.

RocMarshal · 2026-04-08T11:14:13Z

FYI, It would be better to merge it after #27902.

RocMarshal · 2026-04-09T09:11:45Z

flink-tests/src/test/java/org/apache/flink/test/accumulators/AccumulatorITCase.java

            IntCounter simpleCounter = getRuntimeContext().getIntCounter("simple-counter");
            simpleCounter.add(1);
-            Assert.assertEquals(simpleCounter.getLocalValue().intValue(), 1);
+            assertThat(simpleCounter.getLocalValue().intValue()).isEqualTo(1);


Suggested change

assertThat(simpleCounter.getLocalValue().intValue()).isEqualTo(1);

assertThat(simpleCounter.getLocalValue().intValue()).isOne();

Thank you for the comments! I've applied your suggestions, and rebased on the latest master, which already contains #27902

Sorry about that bug!

flink-tests/src/test/java/org/apache/flink/test/misc/MiscellaneousIssuesITCase.java

...ests/src/test/java/org/apache/flink/test/recovery/TaskManagerDisconnectOnShutdownITCase.java

...s/src/test/java/org/apache/flink/test/runtime/TaskManagerLoadingDynamicPropertiesITCase.java

flink-tests/src/test/java/org/apache/flink/test/state/SavepointStateBackendSwitchTestBase.java

…lasses

…lasses 2

RocMarshal · 2026-04-12T02:39:52Z

Reopen for triggering CI.

RocMarshal · 2026-04-12T03:10:29Z

@flinkbot run azure

RocMarshal · 2026-04-13T02:32:47Z

Hi, @mateczagany The CI was failed.
Would you mind helping take a look or re-triggering the CI ?

mateczagany · 2026-04-13T05:50:38Z

@flinkbot run azure

RocMarshal

Thanks @mateczagany

RocMarshal · 2026-04-13T11:07:16Z

Hi, @mateczagany
I found a few of lines un-related to the migration need some minor polish during the review of the current PR.
And created a mini patch to follow it, Could you help take a look ?
Thank you~

#27910

mateczagany marked this pull request as draft February 25, 2026 07:49

mateczagany force-pushed the FLINK-39124-5 branch 2 times, most recently from 049115c to e29e50e Compare February 25, 2026 15:53

mateczagany mentioned this pull request Feb 26, 2026

[FLINK-39124] Update flink-tests to JUnit5 #27657

Closed

RocMarshal self-assigned this Feb 26, 2026

mateczagany marked this pull request as ready for review February 26, 2026 16:17

snuyanzin reviewed Feb 27, 2026

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flink-tests/src/test/java/org/apache/flink/test/accumulators/AccumulatorErrorITCase.java Outdated Show resolved Hide resolved

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flink-tests/src/test/java/org/apache/flink/test/accumulators/AccumulatorITCase.java Outdated Show resolved Hide resolved

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flink-tests/src/test/java/org/apache/flink/test/example/client/LocalExecutorITCase.java Outdated Show resolved Hide resolved

mateczagany force-pushed the FLINK-39124-5 branch from e29e50e to b4c720f Compare March 1, 2026 05:34

snuyanzin reviewed Mar 2, 2026

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snuyanzin reviewed Mar 2, 2026

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mateczagany commented Mar 4, 2026

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github-actions bot added the community-reviewed PR has been reviewed by the community. label Mar 4, 2026

mateczagany force-pushed the FLINK-39124-5 branch from 15db675 to c1efa84 Compare March 18, 2026 14:48

RocMarshal reviewed Apr 9, 2026

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mateczagany added 6 commits April 11, 2026 20:59

[FLINK-39124][test] Migrate remaining flink-tests to JUnit 5

691f8bb

[FLINK-39124] Remove visibility modifiers from all test methods and c…

97fcc10

…lasses

[FLINK-39124] Improve AccumulatorITCase and AccumulatorErrorITCase

414ecaf

[FLINK-39124] Remove visibility modifiers from all test methods and c…

cac6133

…lasses 2

[FLINK-39124] Improve updated test classes

54c714e

[FLINK-39124] Address PR comments

bed5fc4

mateczagany force-pushed the FLINK-39124-5 branch from c1efa84 to bed5fc4 Compare April 11, 2026 19:07

RocMarshal closed this Apr 12, 2026

RocMarshal reopened this Apr 12, 2026

RocMarshal approved these changes Apr 13, 2026

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RocMarshal merged commit 43f81d3 into apache:master Apr 13, 2026

	assertThat(simpleCounter.getLocalValue().intValue()).isEqualTo(1);
	assertThat(simpleCounter.getLocalValue().intValue()).isOne();

Conversation

mateczagany commented Feb 25, 2026

What is the purpose of the change

Brief change log

Verifying this change

Does this pull request potentially affect one of the following parts:

Documentation

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RocMarshal commented Apr 8, 2026

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RocMarshal commented Apr 12, 2026

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flinkbot commented Feb 25, 2026 •

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