[AUDIT] CRITICAL: Increase Test Coverage from 6 tests

Critical: Low Test Coverage

Severity: CRITICAL

Current State

• Only 6 test files found
• Insufficient coverage for production deployment
• Risk of undetected bugs and regressions

Production Architecture Requirements

• TDD: Write tests BEFORE implementation
• Minimum 80% code coverage
• Unit tests: Pure functions, no I/O
• Integration tests: Module boundaries
• E2E tests: User journeys

Required Test Coverage

1. Unit tests for all model functions
2. Integration tests for data pipelines
3. MLflow experiment tracking tests
4. API endpoint tests (if applicable)
5. Validation/schema tests

Required Actions

1. Audit existing codebase for untested code
2. Write unit tests (90% coverage minimum)
3. Write integration tests (80% coverage)
4. Add E2E tests for critical flows
5. Add test coverage reporting to CI/CD
6. Enforce coverage gates in GitLab CI

Test Structure

tests/
├── unit/          # Pure function tests
├── integration/   # Module boundary tests
├── e2e/           # End-to-end flows
└── fixtures/      # Test data

Definition of Done

• Minimum 80% test coverage overall
• 90% coverage on business logic
• All tests passing in CI/CD
• Coverage reports in merge requests
• TDD enforced for new code