I agree, but what if this script takes itself 10 min to run because it has to do lots of work? That's the slow cases I mean. As for tests, of course it's great

I agree, but what if this script takes itself 10 min to run because it has to do lots of work? That's the slow cases I mean. As for tests, of course it's great to have tests, but how do you test if a streaming video from a phone app is dropping more frames after a specific commit? there are things that are hard to test with a script. And usually these are the cases where bisect is very useful, because it reduces two weeks of debugging to two days. Which is still a long time.