GameTest Framework Support

Is your feature request related to a problem?

Currently, PaperMC doesn't support the game test framework. This would allow plugins to have unit-tests to make sure certain behaviors work.

I'll make a quick example, imagine you're working on a plugin that gives mobs levels when they spawn in, so they can be procedurally more challenge. You could then create a game test that spawns a zombie (or some other mob), gives it a level, lets the plugin give it equipment, then check it's equipment.

Describe the solution you'd like.

I think PaperMC should provide API support for the GameTest framework in Minecraft. I don't think it has to mirror the internals exactly, but some sense of compatibility would be nice.

During bootstrapping, you should be able to define:

• Test environments
• Test instances
• Code function tests

Test environments & test instances should probably be exposed through PaperMC's registry system & event lifecycle systems. Code function tests could be registered similarly, but I think the Code Function registry should be based off a Functional Interfaces (so you can use lambdas and define them inline if you'd like).

Describe alternatives you've considered.

You could manually write the tests yourself, but that has a few issues:

• You have to provide the framework yourself
• It (probably) wouldn't integrate nicely into Minecraft's built-in tests.

You could also use NMS, but NMS as far as I'm aware is unsupported officially, and Paper's API should be used wherever possible.

Other

This is natively supported in Minecraft:

• See GameTestHelper class
• https://minecraft.wiki/w/GameTest

This issue would also solve #12331 .
As far as I can tell, this is currently not in the 1.21.5 Todo list at #12289 .

Start by reviewing Minecraft's GameTestHelper class and the linked GameTest documentation, then compare the requested test environments, test instances, and code function tests with Paper's API bootstrap, registry, and event-lifecycle systems. Done means a decided, compatible Paper API design that exposes these GameTest capabilities without requiring NMS.