testing

React tests break during refactors when they assert on internal implementation details instead of user behavior. Testing by user interactions using accessible queries prevents brittle tests and keeps coverage stable across code changes.

Test React components by querying the DOM with accessible selectors like getByRole and getByLabelText in Jest. This validates user behavior and accessibility rather than testing internal state directly.

Mock API calls in React integration tests using MSW to intercept network requests at the service worker level. This allows testing real implementations and async user behavior without modifying internal API logic.

React Testing Library works with TypeScript for hook and component tests, providing comprehensive coverage across leaf and orchestrating components by guiding test structure around real user interactions and waitFor-based async assertions.

Use waitFor for async assertions in React testing when verifying user behavior involving asynchronous operations like API calls. waitFor waits for dynamic DOM updates before asserting, preventing flaky tests in integration scenarios.