[roca]

> most of the time, google could actually do anyway

Maybe you can reproduce the failure once in a while, but can you reproduce it on every run, so that when you apply the debugger to a particular run you're sure to see the failure? That's what rr gives you. Furthermore rr lets you debug the same execution over and over again, so stuff like event ordering and object addresses stay the same between debugging sessions.

And as glandium said, on top of that we build reverse execution, which is a real game-changer. Debugging is about tracing effects back to causes, and reverse-execution is what you actually want for that.

FWIW rr has a fair number of users who find it really does help a lot for all kinds of debugging tasks, not just those involving flaky tests. Some of those users are even at Google :-).