testing-patternslisted

# Testing Patterns > Principles for reliable test suites. --- ## 1. Testing Pyramid ``` /\ E2E (Few) / \ Critical flows /----\ / \ Integration (Some) /--------\ API, DB queries / \ /------------\ Unit (Many) Functions, classes ``` --- ## 2. AAA Pattern | Step | Purpose | |------|---------| | **Arrange** | Set up test data | | **Act** | Execute code under test | | **Assert** | Verify outcome | --- ## 3. Test Type Selection ### When to Use Each | Type | Best For | Speed | |------|----------|-------| | **Unit** | Pure functions, logic | Fast (<50ms) | | **Integration** | API, DB, services | Medium | | **E2E** | Critical user flows | Slow | --- ## 4. Unit Test Principles ### Good Unit Tests | Principle | Meaning | |-----------|---------| | Fast | < 100ms each | | Isolated | No external deps | | Repeatable | Same result always | | Self-checking | No manual verification | | Timely | Written with code | ### What to Unit Test | Test | Don't Test | |------|------------| | Business logic | Framework code | | Edge cases | Third-party libs | | Error handling | Simple getters | --- ## 5. Integration Test Principles ### What to Test | Area | Focus | |------|-------| | API endpoints | Request/response | | Database | Queries, transactions | | External services | Contracts | ### Setup/Teardown | Phase | Action | |-------|--------| | Before All | Connect resources | | Bef