We have this codebase with existing unit tests. When I test just the module I'm adding, all my tests pass. But once I include the tests from the other modules, my tests don't get run anymore. I tried ignoring/skipping some other modules and my tests get included in the runner.

The existing tests sometimes run with 2-3 tests missing (even without the tests I added). I am not sure what causes that, flaky/bad unit tests? Is there any way to check which ones cause that? Or is there a way to completely isolate unit tests so that the existing ones run and so will the newly added ones?