[Backend] Fix test coverage to meet 80% threshold

[Penielka]

Description

Jest config requires 80% coverage but many modules fall below. Add tests to meet coverage thresholds.

Files to Modify

• backend/tests/**/*.test.ts (various)
• backend/jest.config.js

Definition of Done

• Branch coverage >= 80%
• Function coverage >= 80%
• Line coverage >= 80%
• Statement coverage >= 80%
• All critical paths tested
• Edge cases covered
• Error handling tested

Acceptance Criteria

1. npm run test:ci exits with code 0
2. Coverage report shows all metrics >= 80%
3. No skipped tests without documented reason
4. Mock external dependencies appropriately

[Senorespecial]

I would like to work on this issue, pls assign

[Biokes]

Hi maintainer,
I'm a Software Engineer and I'd like to take this issue. I understand the requirements and will follow the existing project structure, keep the implementation clean, and include proper tests where applicable.

[jabir-dev788]

Hey, I’d love to work on this issue if it’s available 🙏
‎I've reviewed this issue and have a clear approach to fix it. I can deliver a clean, minimal PR within 5 hours without touching unrelated code. Happy to take this on if it's still available.

[AbayomiCoded]

I'd like to be assigned to this issue as I have experience writing comprehensive unit and integration tests for NestJS applications to achieve high coverage thresholds across branches, functions, lines, and statements.

[grantfox-oss]

🦊 GrantFox — @AbayomiCoded has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #21)
2. Your PR will be reviewed by the AetherEdu maintainers

Good luck! Track your progress on GrantFox.