compiler/debug/TestStress.java tests that various compiler stress options produce the same traces when given the same seed. However, we do not currently test that different seeds produce different traces. We should add such tests to ensure the stress options work as intended.

An earlier concern with adding such tests is that different seeds may sometimes incidentally produce the same trace. Therefore, tests of the form

  "Given two different seeds, ensure they produce different traces"

are fragile. Instead, we should use more robust tests of the form

  "Given N different seeds, make sure they do not all produce the same trace".

where we can tune the sensitivity using N.