--- name: backend-test-writer description: Use when generating tests for backend code (Express routes, MongoDB models, Node services) - analyzes file type, detects test framework from package.json, generates comprehensive tests with setup\/teardown and edge case coverage --- # Backend Test Writer Generate comprehensive backend tests for MERN stack code. Analyzes file type, detects project conventions, produces tests that actually run. **Philosophy:** Smart defaults, zero config. Detect everything from project. ## Workflow Copy and track progress: - [ ] Phase 0: Infrastructure check - [ ] Phase 1: Analyze target files - [ ] Phase 2: Generate tests - [ ] Phase 3: Report summary ### Phase 0: Infrastructure Check Before generating tests, verify setup: 1. Check `package.json` for test framework (Jest\/Vitest\/Mocha) 2. If none → prompt: "Set up Jest + Supertest?" 3. Check for `mongodb-memory-server` (needed for integration tests) 4. Detect test file convention (colocated vs `__tests__\/` vs `tests\/`) **Stop if:** No test framework and user declines setup. ### Phase 1: Analyze Target Files | Pattern | Type | Test Approach | |---------|------|---------------| | `routes\/`, `*.routes.js` | Route | Integration (Supertest + real DB) | | `controllers\/` | Controller | Integration | | `services\/` | Service | Unit (mocked deps) | | `models\/`, `*.model.js` | Model | Unit (validation tests) | | `middleware\/` | Middleware | Unit (mock req\/res\/next) | | `utils\/`, `helpers\/` | Utility | Unit (pure functions) | **Override:** User can specify `--unit` or `--integration`. ### Phase 2: Generate Tests Process files sequentially with progress. User can stop anytime. **Each test includes:** - Proper imports for detected framework - Setup\/teardown (DB connection, cleanup) - Comprehensive coverage: - Success cases (happy path) - Validation errors (400) - Not found (404) - Auth failures (401\/403) if protected - Edge cases (duplicates, empty, null) **Reference:** See [test-patterns.md](reference\/test-patterns.md) for complete code examples. ### Phase 3: Report ``` Generated: X test files Coverage: Y test cases total Next: Run `npm test` to verify ``` <\/workflow> ## Quick Reference | File Type | Imports | DB Setup | |-----------|---------|----------| | Route | `supertest`, `mongodb-memory-server` | Real (in-memory) | | Service | `jest` | Mocked | | Model | `mongoose` | Mocked | | Middleware | `jest` | None | ## Test Structure Pattern ```javascript describe('[Resource] [Method]', () => { describe('success cases', () => { it('should [expected behavior]', async () => {}); }); describe('validation errors', () => { it('should return 400 for [invalid case]', async () => {}); }); describe('edge cases', () => { it('should handle [edge case]', async () => {}); }); }); ``` <\/quick-reference> ## Checklists ### Infrastructure (Check First) - [ ] Test framework in `package.json` - [ ] Test script defined (`"test": "jest"`) - [ ] Supertest installed (integration tests) - [ ] mongodb-memory-server installed (DB tests) ### Per-File Generation - [ ] Check for existing tests first (gap analysis if found) - [ ] Correct imports for file type - [ ] Setup\/teardown included - [ ] Happy path tested - [ ] Error cases tested (400, 404, 401) - [ ] Edge cases tested (domain-specific: date→DST\/timezone, money→precision, etc.) - [ ] No secrets in assertions - [ ] Async\/await handled properly - [ ] Priority assigned to each test (P0=critical, P1=important, P2=nice-to-have) - [ ] Test helper factories suggested for complex inputs <\/checklists> ## Common Mistakes | Mistake | Fix | |---------|-----| | Starting server in tests | Import app, let Supertest handle it | | No DB cleanup | Add `afterEach` with `deleteMany({})` | | Testing implementation | Test behavior through HTTP interface | | Missing async\/await | Await async operations | | Mocking in integration tests | Use real DB for integration | <\/common-mistakes> ## Guidelines - Don't generate tests for unread code - Don't skip infrastructure check - Don't generate only happy paths - Don't forget cleanup between tests <\/guidelines> ## Reference Files Load when implementing specific patterns: | When | Reference | |------|-----------| | Writing any test | [test-patterns.md](reference\/test-patterns.md) | | Setting up test infrastructure | [test-setup.md](reference\/test-setup.md) | <\/references>