Nested tests in JUnit 6 cause JUnit 5 error

[MaddyGuthridge]

After having my previous report in #1837 unceremoniously and erroneously closed by an AI with no human review, I am opening a new issue to report this bug.

When I have a nested test declaration in a project which uses JUnit 6, attempting to run the test gives an error:

Cannot find org.junit.platform.commons.annotation.Testable on project build path. JUnit 5 tests can only be run if JUnit 5 is on the build path.

As per my project's configuration, we are using JUnit 6, so it is self-evident that JUnit 5 would not be present on the build path. Even if it were present, using it on a project that required JUnit 6 would be incorrect.

Relevant snippet from build.gradle:

dependencies {
    // Use JUnit Jupiter for testing.
    testImplementation 'org.junit.jupiter:junit-jupiter:6.0.1'
    //                                                  ^^^^^
    testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
}

Reproducing

A full reproduction can be found in this repository.

System info

• NixOS 25.11
• VS Code 1.109.2
• Test Runner for Java 0.44.0
• Gradle 9.2.0
• Java 21

This issue has also been reproduced on the systems of many of our students.

Notes

• This issue is not a duplicate, despite the AI's hallucinations.
• The AI's suggested fix in the previous issue did not work to resolve the issue.
• This issue affects me, and hundreds of other students in the course I teach.
• Having an AI automatically close my issue without human review with no way for me to reopen the issue if the AI spits out BS that does not help is an insult to my intelligence.

[github-actions]

Hi @MaddyGuthridge, I'm an AI Support assistant here to help with your issue. While the team reviews your request, I wanted to provide some possible tips and documentation that might help you in the meantime.

Possible causes & fixes

• Missing JUnit Platform classes on the classpath

  • Change your Gradle config to bring in the launcher (and its transitive commons) at compile time rather than only at runtime:

    dependencies {
      testImplementation 'org.junit.jupiter:junit-jupiter:6.0.1'
      testImplementation 'org.junit.platform:junit-platform-launcher'
      // optionally add commons explicitly if still missing
      testImplementation 'org.junit.platform:junit-platform-commons'
    }
    
    test {
      useJUnitPlatform()
    }

  • This ensures org.junit.platform.commons.annotation.Testable is on the test classpath.

• Version support mismatch in the VSCode Java Test extension

  • At present the extension supports JUnit Platform as used by JUnit 5. If you’re on a JUnit 6 milestone, you may see classpath checks fail until JUnit 6 is officially supported.
  • As a temporary workaround, consider reverting to JUnit Jupiter 5.x:

    dependencies {
      testImplementation 'org.junit.jupiter:junit-jupiter:5.10.0'
      testImplementation 'org.junit.platform:junit-platform-launcher:1.10.0'
    }
    
    test {
      useJUnitPlatform()
    }

Relevant issue

• Support other JUnit 5 test engines / support JUnit 5 platform (requests enabling Run/Debug for any @testable meta-annotated classes, including nested):
  Support other JUnit 5 test engines / support JUnit 5 platform #975 (comment)

Other references with low confidence

• @nested subclass tests do not provide inline Run Test | Debug Test links
  • Issue about UI links missing for nested JUnit 5 tests
  • URL: @Nested subclass tests do not provide inline Run Test | Debug Test links #719

The team will respond to your issue shortly. I hope these suggestions are helpful in the meantime. If this comment helped you, please give it a 👍. If the suggestion was not helpful or incorrect, please give it a 👎. Your feedback helps us improve!