We've discussed a wide variety of things concerning PHPUnit such as assertions, data providers, and fixtures. We've seen how to make tests pass and how to preventively catch errors that might cause bigger problems.

There are many more things you can discover on both Codeception unit tests and PHPUnit, but what we've seen up until now should be enough to give you the confidence required to start creating tests with clarity.

In the next chapter, we'll see how to test components that rely on external code and classes, in order to get the best controlled environment needed by using stubs and mocks.