We spent a lot of time exploring the default test library provided by Swift. Testing is an important practice during the development of an app; the strategy we want to follow must be clear so that we can produce the best and most robust app possible. We must put a lot of effort into unit and UI tests, without forgetting to test the app in the ways that it will be used by the customer. We can't always test in isolation, so the test double technique will help us to separate the different parts we want to verify in a practical way.

Now that we've covered all these techniques for testing the software, we are ready to go open source, which means releasing our software in the wild, as we'll see in the next chapter.