That's fuzz testing, not unit testing. Using a fuzz tester to generate a corpus of test cases which are then fixed in unit tests is a good idea. But randomizing

That's fuzz testing, not unit testing. Using a fuzz tester to generate a corpus of test cases which are then fixed in unit tests is a good idea. But randomizing your "quick to run, must pass on every commit" unit tests is problematic for reasons other people have noted in this thread (and very slow).