Integration Test

While unit tests check individual functions, integration tests check that components work together. An integration test might hit a real API endpoint, write to a test database, and verify the response. It tests the wiring between layers, not just isolated logic.

Integration tests are slower than unit tests but catch a different class of bugs: misconfigured routes, broken database queries, incorrect middleware, and serialization issues. Tools like Supertest (for API endpoints) and Testing Library (for React components) are commonly used.

For vibe coders, integration tests are essential for verifying AI-generated features end to end. A unit test might pass for a function, but the integration test reveals that the function is called with the wrong arguments or the API response shape changed.