[zackelan]

It's possible to have both randomness and reproduciblility - generate a random seed, log it, then explicitly seed the RNG. If you encounter a failure you suspect is caused by a particular random seed, temporarily hard-code that seed while you debug it.

The "that's an intermittent failure, just re-run it and it usually passes" attitude is in my experience more likely due to just plain old poorly-written tests, usually with a time.sleep() or something similar that makes them unreliable.