Summary
We’ve just explored test doubles and how they are used to verify interactions with collaborating objects, such as component props (onSave) and browser API functions (global.fetch). We looked in detail at spies and stubs, the two main types of doubles you’ll use. You also saw how to use a side-by-side implementation as a technique to keep your test failures under control while you switch from one implementation to another.
Although this chapter covered the primary patterns you’ll use when dealing with test doubles, we have one major one still to cover, and that’s how to spy on and stub out React components. That’s what we’ll look at in the next chapter.
