Unit testing ensures your production code is relevant. What ensures your testing code is relevant? Come discover mutation testing and make sure your never forget another assert again. In the realm of testing, the code coverage metric is often talked about. However, it doesn't mean that the test has been useful or even that an assert has been coded. Mutation testing is a strategy to make sure that the test code is relevant. In this talk, Nicholas Frankel will explain how code coverage is computed and what its inherent flaw is. Afterwards, he will describe how mutation testing works and how it helps pointing out code that is tested but leave out corner cases. This session also includes a demonstration on PIT, a Java production-grade framework that enables mutation testing.