Why should I mock API calls in React tests?
Because real API calls make tests slow, flaky, and dependent on a network. Mocking lets tests run fast, deterministically, and without external dependencies, giving reliable results every time.
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More FAQs in How to Mock API Calls in React Testing Library Tests
Use jest.fn to mock the global fetch function, jest.mock to mock an API client module at the boundary, or MSW to intercept requests at the service worker level for the most realistic mocking. Wait for async results with findBy or waitFor.
Mock Service Worker intercepts network requests at the service worker level. It is the most realistic way to mock because your app still makes real requests that are intercepted. It works for both tests and development.
After mocking the API, use findBy queries or waitFor to wait for the data to appear, since rendering is async. You can also assert that a loading spinner appears immediately after render, then is replaced by data.
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