The Linux kernel has a set of sets under tools/testing/selftests which we call "Kernel selftests". Read the Linux kernel selftests documentation. Running selftests used to be fast back in the day when we only had a few kernel selftests. But these days there are many kernel selftests. Part of the beauty of Linux kernel selftests is that there are no rules -- you make your rules. The only rules are at least explicitly mentioning a few targets for Makefiles so that the overall selftests facility knows what target to call to run some tests. Part of the complexity in selftests these days is that due to the lack of rules, you may end up needing a bit of dependencies installed on the target node you want to run the tests on. Kdevops will take care of that for you, and so selftests support are added by each developer which wants to help make this easier for users. Today there is support for at least 3 selftests:
make selftestsmake selftests-baseline
You can also run specific tests:
make selftests-firmwaremake selftests-kmodmake selftests-sysctl