RFR: 8369049: [TestBug] Update JUnit to Version 6.0.0

[Andy Goryachev]

On Thu, 2 Oct 2025 15:45:33 GMT, Marius Hanl <mhanl at openjdk.org> wrote:

> JUnit 6.0.0 is out and we can consider updating to it.
> 
> Release Notes: https://docs.junit.org/current/release-notes/index.html#release-notes-6.0.0
> 
> Notes:
> - Java 17 is the baseline (so not a problem for us, since we have a higher baseline)
> - Deprecation were removed (not a problem, as we don't rely on any)
> - JUnit Vintage Engine is deprecated (not a problem, as we dropped support for it some months ago)
> 
> JUnit 6 now uses a single version number for all dependencies, that is platform, jupiter and vintage (which we do not use anymore). That makes updating it easier.
> 
> It also uses `JSpecify`, which is an annotation library for `@NonNull` and `@Nullable`. All version numbers for JUnit now use a single variable.

I would suggest we postpone the migration to junit6 until after Eclipse provides support for it (screenshot taken with Eclipse Version: 2025-06 (4.36) Build id: I20250528-1830):

<img width="1230" height="716" alt="Screenshot 2025-10-02 at 10 46 25" src="https://github.com/user-attachments/assets/ff6380fa-a81b-4f89-8fca-3adc3ec02475" />

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PR Comment: https://git.openjdk.org/jfx/pull/1925#issuecomment-3362340093