At a previous job, with a huge C++ codebase and ~100 developers over 20 years, many platforms supported, a build could take hours, and the test suite took so long to run that it would take several days or weeks of real time to get through it all.
This cycle time combined with occasional unexpected interactions between components meant that in every release cycle, there were dozens of complicated failing tests where it was not obvious which code change was responsible.
`bisect` here was extremely helpful: instead of having to pore over commit history and think very hard, I could bisect with a small wrapper script that would build and run the failing test in question. Builds still took hours, but I could usually autonatically pinpoint the responsible code change for one of the tests overnight.
(This was not using Git, but Perforce, for which I had to write `p4-bisect`. Alas, it's not open-source...)
> in every release cycle, there were dozens of complicated failing tests
Sorry if this is a dumb question, perhaps I'm not understanding what you mean by every release cycle, but does this mean nobody in the team/company ran tests until it was time for release? That sounds like a really big everlasting wound to put a tiny git-bisect bandage on!
> does this mean nobody in the team/company ran tests until it was time for release?
The OP wrote “many platforms supported, a build could take hours, and the test suite took so long to run that it would take several days or weeks of real time to get through it all”
⇒ I think they did run tests, but typically not all of them on all platforms.