test-coverage

Test Coverage

Analyze current test coverage, identify gaps, and write tests to achieve at least 80% coverage.

Steps

1. Run the test suite with coverage enabled:

   • Detect the test runner (jest, vitest, pytest, go test, etc.).
   • Run with coverage flags and capture the coverage report output.

   npm test -- --coverage
   pytest --cov --cov-report=html
   go test -cover -coverprofile=coverage.out ./...
   

2. Parse the coverage report:

   • Identify files below 80% coverage.
   • Sort by coverage percentage (lowest first).
   • Note which lines and branches are uncovered.

3. Prioritize coverage gaps:

   • Focus on business logic and utility functions first.
   • Prioritize files with complex branching and error handling.
   • Skip auto-generated files, type definitions, and configuration files.

4. Write missing unit tests:

   • For each uncovered function, write tests covering:
     • Happy path with valid inputs.
     • Edge cases (null, undefined, empty, boundary values).
     • Error cases (invalid inputs, thrown exceptions).
   • Follow existing test patterns and conventions in the project.
   • Use descriptive test names that explain the expected behavior.

5. Write missing integration tests:

   • Test API endpoints with valid and invalid requests.
   • Test database operations with proper setup and teardown.
   • Test interactions between modules.

6. Run tests after writing each batch:

   • Verify new tests pass.
   • Verify existing tests still pass.
   • Re-check coverage numbers.

7. Repeat until all target files are at or above 80% coverage.

If Coverage Cannot Reach 80%

• Check if uncovered code is truly unreachable (dead code) and remove it.
• Check if uncovered code requires complex setup (external services, specific environments) and note it.
• Document any intentional exclusions with coverage ignore comments and justification.

Output

Updated test suite with all tests passing and coverage at or above 80% for target files. Include a before/after coverage summary.