To test your code properly, you must learn how to lie to it. Mocking is the art of creating fake dependencies.
1The Power of Spies
Spies are like silent observers. They don't change how your code runs, but they record every move. They are perfect for testing 'side effects' like logging or analytics.
2Stubs: Controlling the Narrative
Does your app behave correctly when the database is down? Instead of unplugging your server, use a Stub to force a 'Connection Error' and see if your app handles it gracefully.
3Mocks: Verifying Intent
Mocks are more than just fake functions; they are behavioral contracts. They ensure that your logic doesn't just produce the right output, but also interacts with its environment correctly.
