junit5vintage provider resolves junit-platform-launcher to a JUnit line its vintage engine cannot wire to

[khatchad]

Environment

• Tycho 5.0.2, Maven 3.9.11, Java 25
• Target platform based on the Eclipse 4.39 SimRel repository, which ships two JUnit lines side by side: jupiter 5.14.3/platform 1.14.3/vintage 5.14.3, and jupiter+platform 6.0.3 with no vintage engine at 6.x
• An eclipse-test-plugin module whose tests are JUnit 4 (org.junit;bundle-version="4.13.2" in the test bundle), configured with <providerHint>junit5vintage</providerHint> to gain -Dtest=Class#method selection

Observed

Provider selection succeeds, but the assembled test runtime carries both JUnit lines: junit-platform-launcher resolves to 6.0.3 while junit-vintage-engine resolves to 5.14.3, which wires junit-platform-engine 1.14.3. Both version sets appear in the runtime's config.ini. Discovery then fails with:

java.util.ServiceConfigurationError: org.junit.platform.engine.TestEngine: org.junit.jupiter.engine.JupiterTestEngine not a subtype

The run aborts having executed zero tests (launcher exit code 13).

Expected

The provider constrains the platform/launcher resolution to the range its maximum available vintage engine can wire to, or fails resolution with a diagnostic naming the two lines. Assembling a runtime whose ServiceLoader spans two incompatible copies of TestEngine produces a failure that points at JUnit internals rather than at the resolution that caused it.

Other Providers Against the Same Target

• junit5vintageinternal refuses to resolve: its supported range is [5.0.0,5.12.0), below every JUnit version the 4.39 repo ships.
• junit6 launches a coherent 6.0.3 runtime but discovers no JUnit 4 tests, since the repo carries no 6.x vintage engine. That combination leaves no working provider for JUnit 4 test bundles against this SimRel until a 6.x vintage engine ships.

Cross-Refs

Consumer-side diagnosis matrix: ponder-lab/Hybridize-Functions-Refactoring#749 (comment)

[laeubi]

Environment
Tycho 5.0.2, Maven 3.9.11, Java 25

Please try latest Tycho 5.03 release and the current tycho snapshot build.

[khatchad]

Retested on both. The failure reproduces unchanged on Tycho 5.0.3 and on the current snapshot (6.0.0-SNAPSHOT, build 6.0.0-20260805.205143, from the tycho-snapshots repository), the latter under Maven 3.9.16 since main requires 3.9.12+. In both cases the assembled test runtime again carries both JUnit lines from the 4.39 SimRel repository (junit-platform-launcher resolves to 6.0.3 alongside 1.14.3, junit-vintage-engine to 5.14.3 only), and discovery fails with the same ServiceConfigurationError: org.junit.jupiter.engine.JupiterTestEngine not a subtype, executing zero tests. I can rerun against a branch or patched snapshot if that helps.

[laeubi]

Have you made sure that the import range is correctly excluding junit 6 in your test bundles?

[khatchad]

Yes. The test bundle imports no JUnit platform or jupiter packages; at the time of the report its only JUnit dependency was Require-Bundle: org.junit;bundle-version="4.13.2".

JUnit 6 enters through the target platform instead: the bundle requires org.eclipse.jdt.ui.tests.refactoring, which via org.eclipse.jdt.ui.tests non-optionally requires org.eclipse.jdt.junit6.runtime, and that requires the whole 6.x line at [6.0.0,7.0.0). Filtering the 6.x line out of the target makes resolution fail on exactly that requirement, so both lines end up in the runtime no matter what our bundle declares.

We have since worked around it: providerHint junit6, Central's junit-vintage-engine:6.0.3 in the target (the SimRel ships no 6.x vintage engine), and a Require-Bundle on the engine so the booter's discovery sees it. That runs our JUnit 4 suite green, so the current repository state differs from the reported configuration.