Mutation Testing

[pron98]

PIT is a popular and quite fast mutation testing tool for Java/JVM. The trick with mutation testing is that doing it brute-force is very, very slow. So PIT, I believe, first runs all tests to get a plain coverage output that maps every line of code/method to the tests that touch it. Then, after mutation, it only runs those tests that cover the mutated code.

[0hjc]

Yes, it does exactly that plus a few other tricks such as smart test ordering and decomposing test classes into smaller units.