[Backend]: Add unit tests for all service modules (zero coverage today) #68

🧭 Project Area

Testing / Quality

📝 Issue Summary and Problem Description

Issue summary:
The six backend service modules — auth, documents, verifications, vault, notifications, search — have zero unit test coverage. The entire test suite consists of only 19 tests across 3 files (1 integration, 2 unit), and none test any service-layer business logic.

Current test inventory:

Problem description:
The service layer contains the core business logic: password hashing, token generation, document verification (SHA-256 hash comparison), vault sharing/invitation flows, email notifications, and full-text search. Without tests:

• Regressions in critical security logic (auth, verification) go undetected
• Refactoring carries high risk
• New contributors lack test examples to follow
• CI provides a false sense of coverage

Who is affected:
All developers and users. Lack of test coverage directly impacts software reliability and developer confidence.

🔍 Current and Expected Behaviour

Current behaviour:

• auth.service.ts — 0 tests (register, login, refresh, forgotPassword, resetPassword, verifyEmail, resendVerification)
• document.service.ts — 0 tests (CRUD, upload, verify, search, filter, archive, favorite, summary)
• verification.service.ts — 0 tests (verifyDocument, revokeVerification, getVerificationByHash)
• vault.service.ts — 0 tests (invite, accept, decline, leave, getVaultMembers)
• notification.service.ts — 0 tests (createNotification, getNotifications, markAsRead)
• search.service.ts — 0 tests (fullTextSearch, filterDocuments)

Expected behaviour:
Each service has unit tests covering happy path, error paths, and edge cases.

🧩 Reproduction and Evidence

Step 1: Run `cd backend && npm test`
Step 2: Observe 19 passing tests
Step 3: Check coverage — no service files are tested

Evidence:

• backend/tests/ directory contains only 3 test files
• backend/src/modules/auth/auth.service.ts — 15+ exported functions, 0 tests
• backend/src/modules/documents/document.service.ts — 15+ exported functions, 0 tests

🎯 Affected Scope

Affected files (new test files to create):

• backend/tests/unit/auth.service.test.ts
• backend/tests/unit/document.service.test.ts
• backend/tests/unit/verification.service.test.ts
• backend/tests/unit/vault.service.test.ts
• backend/tests/unit/notification.service.test.ts
• backend/tests/unit/search.service.test.ts

Affected APIs: All API endpoints (service tests validate the underlying business logic)
Database changes required? Yes — tests should use mongodb-memory-server

🖥 Environment

Operating system: All
Node.js version: v22.x
Package manager: npm 10.x
Deployment environment: Local development and CI

💡 Solution, Alternatives, and Estimate

Priority: P1 High
Proposed solution:

1. Install mongodb-memory-server (if not already a dev dependency)
2. Create per-service test files under backend/tests/unit/
3. For database-dependent tests (document, verification), use mongodb-memory-server
4. For auth service tests, mock the database or use in-memory MongoDB
5. Each test file covers: happy path, error paths, edge cases

Alternative solutions:
Could be split into 6 separate issues (one per service) to allow parallel contributions.

Difficulty: Advanced
Estimated time: 20-30 hours (across all 6 services)
Dependencies or blockers: mongodb-memory-server package

✅ Acceptance Criteria and Additional Notes

• auth.service.ts has tests for register, login, refreshToken, forgotPassword, resetPassword
• document.service.ts has tests for create, findById, update, delete, search, filter, getSummary
• verification.service.ts has tests for verifyDocument, revokeVerification, getVerificationByHash
• vault.service.ts has tests for invite, accept, decline, leave
• notification.service.ts and search.service.ts have basic happy-path tests
• All 19 existing tests continue to pass
• Test files use node:test and node:assert (consistent with existing tests)

Additional notes:
This is a large task that could be split into multiple issues (one per service) to allow parallel contributions by different developers.

🤝 Contributor Checklist

• I have searched existing issues and pull requests for duplicates.
• I can reproduce the issue, or I have clearly explained why reproduction is not applicable.
• I will follow the contribution guidelines and target ecsoc-2026.
• I agree to follow the Code of Conduct.
• I have removed secrets, private documents, and personal data.