[Feature Request] Support JUnit 5

[dbwiddis]

Is your feature request related to a problem? Please describe

Many plugins use JUnit5 for unit testing..

However, OpenSearch is still using JUnit 4, which is the version available in the version catalog:
https://github.com/opensearch-project/OpenSearch/blob/main/gradle/libs.versions.toml#L64

This results in a lot of version bump PR churn.

Describe the solution you'd like

1. Add (the latest) junit5 version to the version catalog
2. Add some minimal code somewhere in the OpenSearch repo that will trigger dependabot to keep that version updated.
3. Consider now, or in the future, making alternative versions of OpenSearch test framework classes that depend on JUnit 5

Related component

Build

Describe alternatives you've considered

1. We could just add the version to the version catalog. This is a very simple solution that would allow plugins to reduce their version bump PR churn, but would (probably) not automatically update via dependabot.
2. We could consider updating the OpenSearch test framework classes to depend on JUnit 5 as part of 3.x release

Additional context

Option 3 and alternative 2 are probably not easy, requiring upstream changes:

• Add support for JUnit5 randomizedtesting/randomizedtesting#256

[andrross]

@dbwiddis I'm all for avoiding the PR churn you highlighted here. I honestly don't know the pros/cons of the solutions you listed.

Would option 2 be something like creating a :test:framework-junit5 module in the core that has a JUnit5 dependency? Plugins could optionally take a dependency on that and there would be a single place where that version would get updated by dependabot. Please feel free to take a stab at prototyping one of these options if it seems feasible.

[andrross]

Or could we just add a JUnit5 dependency to :test:framework if JUnits 4 and 5 are happy to live side-by-side?

[dbwiddis]

I'll take a stab in my free time at what some of the current uses are and see if I can have a minimal JUnit5 Superclass to give at least some of the benefits.

[dbwiddis]

After initial research it may be as simple as just brining in JUnit5 dependency (thus getting the version) and using the vintage engine to run existing JUnit4 code/tests, with no additional tests needed.

[dbwiddis]

Or could we just add a JUnit5 dependency to :test:framework if JUnits 4 and 5 are happy to live side-by-side?

Went with this approach. See https://junit.org/junit5/docs/current/user-guide/#migrating-from-junit4

By adding the "vintage" engine, existing Junit 4 tests/code continue to run and allow a slow migration (or partial migration).

[dbwiddis]

Closing, see discussion on #17745