[AstralStorm]

How do you know which is failing without exhaustive analysis?

See, once you know why the test fails and it's not the tested application, which is exceedingly rare in practice, you can just disable it or fix it. But only if you're actually sure, not before.

[muro]

In my experience it is usually the test.

[lukego]

In my experience that's because tests are usually written in a timid style that tries not to provoke flaky behaviour from applications.

If your test suite can handle non-determinism then you can approach test-writing in a completely different - braver - way.