Effective tests give confidence without slowing development. Here's how to test React applications.
Testing Philosophy
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Component Testing
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Async Testing
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Mocking
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Testing Hooks
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Testing with Context
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Integration Tests
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MSW for API Mocking
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Snapshot Testing
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Accessibility Testing
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Best Practices
Principles:
✓ Test behavior, not implementation
✓ Write tests from user perspective
✓ Use semantic queries (getByRole, getByLabelText)
✓ Avoid testing internal state
Organization:
✓ One assertion per test when possible
✓ Use descriptive test names
✓ Group related tests with describe
✓ Keep tests independent
Performance:
✓ Mock expensive operations
✓ Use beforeEach for setup
✓ Clean up after tests
✓ Run tests in parallel
Coverage:
✓ Focus on critical paths
✓ Test error states
✓ Test edge cases
✓ Don't chase 100% coverage
Conclusion
Effective React testing focuses on user behavior rather than implementation details. Use Testing Library's semantic queries, mock external dependencies with MSW, and test hooks with renderHook. Write integration tests for critical flows and keep tests maintainable by avoiding implementation details.