I still think that tests would be flaky without complete isolation in a different database instances. Transaction isolation is nice, but for serial isolation yo

I still think that tests would be flaky without complete isolation in a different database instances. Transaction isolation is nice, but for serial isolation you would get errors when you can't commit that transaction and you'll need to repeat the test (which might cause further issues) and for lesser isolation levels you would get some phantom reads which might manifest as a rare test failures which is a terrible thing, because you can't reproduce it.