Integration Testing: Testing Components Together

Integration tests verify that components work correctly together. This guide covers patterns for testing real interactions.

API Integration Tests#

Testing Express Routes#

Testing Authentication#

Database Integration Tests#

Using Test Containers#

Transaction Testing#

External Service Integration#

Using MSW for API Mocking#

Redis Integration#

Best Practices#

1. Use real databases in containers: More realistic than mocks
2. Clean up between tests: Prevent test pollution
3. Test failure scenarios: Network errors, timeouts, invalid data
4. Keep tests focused: One integration point per test
5. Use factories for test data: Consistent, maintainable setup

Conclusion#

Integration tests verify real interactions between components. Use test containers for databases, MSW for external APIs, and ensure proper cleanup between tests. Balance coverage with test execution time.