mutation tests would be magical fast, they would point to two interesting pieces of your code – not necessarily broken, just interesting
tests are code without tests – what about mutating them? Does that make them more tested?
Think about tests that don't actually test what you think they do, and how you have to add the negative test to ensure that it is testing what you think it is (like testing-concept-force-failure)
fuzzing is like mutation testing but only mutating the inputs
"Refactoring makes you smarter. Refactoring basically gives you an exobrain. So you offload a bunch of those little details that under normal circumstances go into working memory into your tests. Once you start refactoring you start reclaiming your brain."