Dave is a semi-retired software development consultant (writing code \*and\* giving advice about it), with 39 years of professional experience in a wide variety of languages, techniques, domains, etc. He is the T. Rex of Codosaurus, LLC (his one-person consulting firm, which explains how he can get such a cool title, at <https://www.Codosaur.us/>) near Washington, DC, USA. His main focus in software lately is to spread the gospel of quality, including defining what that even means, and talking about techniques to achieve it. In his spare time, he brews mead, teaches others how -- and speaks at conferences, in English and Portuguese.

Would your test suite still pass if the tested code was changed? If so, there may be problems with your code, your tests, or both! Mutation Testing reveals these cases. This talk will tell you what mutation testing is, how it works, how to use it, and its benefits, drawbacks, and history. There will be multiple examples, and a list of tools for many languages. You will come away equipped with a powerful technique for making sure your test suite is strict and your code is meaningful!