feat: Migrate to JUnit 5 and add parallel test execution

[AbgarSim]

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Fixes #4041 ☕️

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[gemini-code-assist]

Summary of Changes

Hello @AbgarSim, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request undertakes a significant modernization effort by migrating the project's testing infrastructure from JUnit 4 to JUnit 5. This transition not only updates the core testing framework but also introduces parallel test execution, aiming to drastically improve the speed and efficiency of the test suite. The changes span across dependency management, test class annotations, and assertion method usage, ensuring full compatibility with the latest JUnit platform features.

Highlights

• Migration to JUnit 5: The project's testing framework has been upgraded from JUnit 4 to JUnit 5. This involved updating core JUnit dependencies and adapting test annotations and assertion methods across numerous test files to align with the JUnit 5 API.
• Parallel Test Execution: Parallel execution of tests has been enabled by introducing a junit-platform.properties file. This configuration sets up concurrent execution for test classes and methods with a fixed parallelism of 8, aiming to significantly improve test suite performance.
• Mockito Integration Update: Mockito integration has been updated for JUnit 5 by adding the mockito-junit-jupiter dependency. Existing @RunWith(MockitoJUnitRunner.class) annotations were replaced with @ExtendWith(MockitoExtension.class) to ensure compatibility and leverage JUnit 5's extension model.
• Assertion Modernization: JUnit 4 static assertion methods from org.junit.Assert (e.g., assertEquals, assertNotNull, fail) have been replaced with their JUnit 5 counterparts from org.junit.jupiter.api.Assertions for improved readability and consistency.
• Lifecycle Method Updates: JUnit 4 test lifecycle annotations such as @Before and @BeforeClass have been migrated to their JUnit 5 equivalents, @BeforeEach and @BeforeAll respectively, providing clearer semantics for test setup and teardown.

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[gemini-code-assist]

Code Review

This pull request does a great job migrating the project to JUnit 5 and enabling parallel test execution. The changes in pom.xml and the introduction of junit-platform.properties are correct.

However, the migration of the test source code is incomplete. Many test files still use assertions from JUnit 4 (org.junit.Assert), which can lead to a mixed test dependency setup. For a clean migration, it's best to consistently use JUnit 5's assertions from org.junit.jupiter.api.Assertions.

I've left a few specific comments to highlight this issue. A global search-and-replace for org.junit.Assert imports should help clean this up across the codebase.

[lqiu96]

Our SDK actually manages a set of common dependencies upstream here: https://github.com/googleapis/sdk-platform-java/blob/b68791d074c02e02a5ccf2f937a5922749a14f56/gapic-generator-java-pom-parent/pom.xml#L40 (a bit of a convoluted process to get here).

You should be able to reference the ${junit.version} there so it's centrally managed.

[AbgarSim]

So I'm not quite sure how this repo is linked to gapic-generator-java-pom-parent and just using ${junit.version} fails locally.

However, following the trail of parents of this repo i was able to reach native-image-shared-config pom which has <junit-vintage-engine.version>5.11.4</junit-vintage-engine.version>

I used this placeholder instead, please advice if this is acceptable or how to reach ${junit.version}

[lqiu96]

Thanks again @AbgarSim, really appreciate the work going into migrating to JUnit 5! The tests generally look good. I added a few comments mostly about dependencies.

For the the wildcard imports (import static org.junit.jupiter.api.Assertions.*;, can you break them down into the individual imports that are used?

Additionally, we have the dependencies check reporting:

Error:  Used undeclared dependencies found:
Error:     org.junit.jupiter:junit-jupiter-api:jar:5.11.4:test
Error:     junit:junit:jar:4.13.2:test
Error:  Unused declared dependencies found:
Error:     org.junit.jupiter:junit-jupiter:jar:5.11.4:test

[AbgarSim]

Hi @lqiu96 thanks for the feedback!

I've pushed the following adjustments:

• Deleted junit-platform.properties - will move it as separate PR
• Adjusted all the Assertion.* imports, good catch missed those
• Used the junit-vintage-engine.version for junit dep - as per my comment above please advice if this is ok
• Split JUnit Jupiter into explicit junit-jupiter-api and junit-jupiter-engine, this should address the dependencies check