Well, the problem is that I just don't get any output from this. I would normally just do some tests to figure out where the problem lies, but I was hoping someone would be able to tell me a ...

Even more important, putting all the tests together in a test suite provides for regression testing—before any new code is committed, all pre-existing tests should pass.

Sebastian Bergmann, author of PHPUnit, talks in an interview about highlights and preparation tips for the release of version 12 in February 2025.