How do I test error handling in a React component?
Mock a rejected promise from the API and assert that your UI shows the error message and a retry option, not a blank screen. This confirms your error handling works for real users when the API fails.
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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.
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.
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.
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