Test Coverage Analyzer

Analyze test coverage and generate tests to fill gaps.

Workflow

1. Run coverage analysis:

   • Detect the test framework and run with coverage enabled:
     • JS/TS: npx jest --coverage or npx vitest --coverage or npx nyc mocha
     • Python: pytest --cov=<package> --cov-report=term-missing
     • Go: go test -coverprofile=coverage.out ./... && go tool cover -func=coverage.out
     • Rust: cargo tarpaulin or cargo llvm-cov
   • Parse the coverage output.

2. Analyze coverage gaps:

   • Identify files with lowest coverage.
   • Identify uncovered lines and branches.
   • Categorize gaps:
     • Critical: Business logic, data validation, security checks.
     • Important: Error handling, edge cases.
     • Low priority: Logging, formatting, simple getters/setters.

3. Present a coverage report:

Coverage Summary: XX.X% (target: YY%)

Critical Gaps:
  src/auth/login.ts        45%  — lines 23-40, 67-89 (authentication logic)
  src/api/payments.ts      38%  — lines 12-35 (payment processing)

Important Gaps:
  src/utils/validator.ts   62%  — lines 44-58 (error handling)

Files at 100%: 12/30

4. Generate tests for the highest-priority gaps:

   • Start with critical business logic.
   • Focus on untested branches and error paths.
   • Follow the project's existing test patterns.

5. Re-run coverage to verify improvement.

Guidelines

• Focus on meaningful coverage, not just hitting a number.
• 100% coverage doesn't mean bug-free — test quality matters more than quantity.
• Prioritize branch coverage over line coverage.
• Don't test trivially obvious code just for the coverage number.
• If coverage tooling isn't set up, help configure it first.
• Consider setting up coverage thresholds in CI config if not already present.