feat add testing

backend/README.md

@@ -0,0 +1,81 @@
+## Running tests (ALJ)
+
+The file `backend/src/tests/tests-ALJ.test.ts` contains both unit and integration suites.
+
+- **Unit tests** are fully mocked (no Docker, no DB):
+  ```bash
+  cd backend && npm run test:unit
+  ```
+- **Integration tests** spin up a disposable PostgreSQL via Testcontainers and run real Prisma migrations against it. Docker must be running:
+  ```bash
+  cd backend && npm run test:integration
+  ```
+- **Everything**:
+  ```bash
+  cd backend && npm run test:all
+  ```
+
+First integration run pulls the `postgres:latest` image (~671 MB). Subsequent runs reuse the cached image; container boot is ~1 s and a full `test:all` finishes in ~3 s on a warm cache.
+
+### macOS / Docker Desktop note
+
+The integration suite sets `process.env.TESTCONTAINERS_RYUK_DISABLED = 'true'` in its `beforeAll`. Ryuk is Testcontainers' cleanup sidecar and fails to reach the Docker daemon socket on some Docker Desktop configurations on macOS. Container cleanup is still deterministic via the suite's `afterAll → container.stop()`. If Jest is killed mid-run (rare), a leftover postgres container can be cleaned up with `docker container prune`.
+
+### Schema bootstrap: `db push` vs `migrate deploy`
+
+The integration suite uses `npx prisma db push --skip-generate --accept-data-loss` rather than `migrate deploy`. `db push` applies `prisma/schema.prisma` directly to the disposable container, bypassing the `prisma/migrations/` folder. This means the test suite works even if the migrations folder is empty or out of sync with the schema (which is the case if you've ever run `prisma migrate reset` without re-creating an init migration). If you regenerate migrations with `prisma migrate dev`, the test suite remains unaffected.
+
+### Why `app.listen` doesn't bind a port during tests
+
+`src/index.ts` calls `app.listen(3010)` unconditionally. Both test suites stub `express.application.listen` to a no-op inside their `jest.isolateModules` blocks before requiring the app. This prevents the test process from competing with the dev server (or stale prior test runs) on port `3010`. Supertest is unaffected because it uses `http.createServer(app).listen(0)` directly, not the express prototype method.
+
+### Test inventory
+
+**30 tests total — 22 unit + 8 integration.**
+
+#### `UNIT — mocked, no database`
+
+**Validator (`validateCandidateData`) — 7**
+
+1. accepts a fully valid candidate payload
+2. rejects missing `firstName`
+3. rejects missing `lastName`
+4. rejects invalid email format
+5. rejects invalid phone format (must match Spanish 6/7/9 + 8 digits)
+6. rejects malformed `educations[].startDate`
+7. rejects `cv` missing `fileType`
+
+**Domain models — 4**
+
+8. `Candidate.save()` (no id) calls `prisma.candidate.create` with flat fields and no nested writes
+9. `Education.save()` (new) calls `prisma.education.create` with the `candidateId` linkage
+10. `WorkExperience.save()` (new) calls `prisma.workExperience.create` with the `candidateId` linkage
+11. `Resume.save()` persists `filePath`, `fileType`, `candidateId`, and a generated `uploadDate`
+
+**Service (`addCandidate`) — 4**
+
+12. happy path: validates, then saves Candidate + each Education + WorkExperience + Resume
+13. validator failure short-circuits: throws and never calls Prisma
+14. Prisma `P2002` (unique-email) is mapped to "email already exists" domain error
+15. empty `educations` and `workExperiences` arrays do not trigger nested creates
+
+**Routes — `POST /candidates` via supertest (also covers controller-equivalent behaviour) — 7**
+
+16. valid body → 201, body equals service's return value
+17. valid body invokes the service exactly once with the request body
+18. service throws `Error("Invalid email")` → 400 with the error message
+19. service throws "email already exists" Error → 400 with that message
+20. service throws a non-Error (string) → 500 with "unexpected" message
+21. `GET /unknown-route` → 404
+22. `GET /` (root) → 200 with the LTI greeting (sanity check that the app booted)
+
+#### `INTEGRATION — Testcontainers + Prisma + supertest` — 8
+
+23. `POST /candidates` creates a candidate with educations, workExperiences, and resume
+24. `POST /candidates` twice with the same email → second is rejected, only one row in DB
+25. `POST /candidates` with invalid email → 400 and zero rows persisted
+26. `POST /candidates` with empty `educations` and `workExperiences` arrays → 201, candidate row exists, zero child rows
+27. repository: `Candidate.save()` against real Prisma — row appears, ids autoincrement
+28. referential integrity: deleting a candidate with children fails (schema is `onDelete: RESTRICT`)
+29. date handling: ISO date strings in the request body are stored as `DateTime` columns and roundtrip
+30. CV persistence: payload's `cv` produces a linked resume row (no real disk write)

backend/package.json

@@ -25,19 +25,24 @@
         "swagger-ui-express": "^5.0.0"
     },
     "devDependencies": {
+        "@testcontainers/postgresql": "^11.14.0",
         "@types/cors": "^2.8.17",
         "@types/express": "^4.17.9",
         "@types/jest": "^29.5.13",
         "@types/multer": "^1.4.11",
         "@types/node": "^20.12.10",
+        "@types/supertest": "^7.2.0",
         "eslint": "^9.2.0",
         "eslint-config-prettier": "^9.1.0",
         "eslint-plugin-prettier": "^5.1.3",
         "jest": "^29.7.0",
+        "jest-mock-extended": "^4.0.1",
         "prettier": "^3.2.5",
         "prisma": "^5.13.0",
+        "supertest": "^7.2.2",
+        "testcontainers": "^11.14.0",
         "ts-jest": "^29.2.5",
-        "ts-node": "^9.1.1",
+        "ts-node": "^10.9.2",
         "ts-node-dev": "^1.1.6",
         "typescript": "^4.9.5"
     }