Who watches the watchmen?

Software developers write tests to ensure their code is working correctly. These tests allow us to confidently work on unfamiliar code, and make broad changes without worrying (too much) about breaking everything.

Without them, we would be lost; struggling through a world where honest mistakes cause massive headaches. They serve as documentation, as reassurance, and as guidance.

But how do you know if your tests are any good?

Mutation testing is a strategy that can help you evaluate the effectiveness of your test suite. By making modifications to your code, mutation testing can tell you which tests don’t fail when they should, and give you a starting point to writing better tests.