You have written plenty of tests. Your test code is well-organized, runs regularly, and the reporting is top-notch. But how do you know that your tests are doing their job and finding bugs before your users do? In this talk, we will have a look at test quality in Python projects. What are good tests for Python codebases? Where should we focus our testing effort? How do we make our tests maintainable? What role should coverage play in looking at a test codebase? Can code mutation help us gain insight into the quality of our test base? After many years of Python and software quality work, I want to give you some additional ideas about good tests in Python that you can hopefully apply to your own tests.