is there a plugin for continuous testing, as Ncrunch for C#? the auto-test function in Intellij is not as useful

None that I know of. I usually don't do that kind of thing, could you elaborate a little bit more? Do you want tests to be running like every 5 seconds after you compile?

I would like tests to be run when I edit code, and just run the tests that exercise the changed code.

Auto test / auto compile & reload is one of those areas where the JVM feels like it's a long way behind the node ecosystem where it's table stakes.

This would be super nice to have continuous feedback.