We all know that unit tests help us to be sure code works as we expected. And one of the metrics we can use with unit tests is a Code Coverage. But is it a good metric? Does it have a practical sense and can we really trust it?
How confident are you in the project’s test suite? Does it cover all the branches of the code? Does it test anything at all?
This talk answers to these questions and gives quite a deep introduction to Mutation Testing methodology, describes how it can be used, and how developers can get started working with it. It also describes the issues of Code Coverage and introduces Infection library - Mutation Testing framework for PHP.