The Purpose of Code Tests

Sometimes, we’ll find parts of the code that we don’t fully trust, even after carefully writing it. It could be that someone else wrote it, and we don’t trust our understanding of it. In either case, testing should help. The subject of the next four chapters is what to test, how to test, and how to manage those tests. Testing works best in the small and in the large, but not in-between.

Testing a collection of functions

It’s useful to test a function and an entire use case of an application, but testing a collection of functions is problematic for two reasons: