Integration Testing

Unit tests prove logic works. Integration tests prove logic works together.

The Database Strategy

How to test code that reads/writes to SQL?

1. In-Memory (SQLite): Fast, but risky. SQLite behaves differently than Postgres (e.g., missing JSONB functions).
2. Docker Containers (Testcontainers): Spin up a real Postgres container for the test suite.
   • Setup: Start container -> Run Migrations -> Run Tests -> Destroy.
   • Verdict: The modern standard. Slightly slower, but 100% accurate.

API Testing

Testing your REST/GraphQL endpoints via HTTP calls (e.g., using Supertest).

• Scope: Send request -> Check Response Code -> Check DB side effects.
• Mocking: You usually mock external 3rd party APIs (Stripe, Twilio) but keep your internal Database real.