Test coverage

--- description: Analyze coverage, identify gaps, and generate missing tests toward the target threshold. --- # Test Coverage Analyze test coverage, identify gaps, and generate missing tests to reach 80%+ coverage. ## Step 1: Detect Test Framework | Indicator | Coverage Command | |-----------|-----------------| | jest.config.* or package.json jest | npx jest --coverage --coverageReporters=json-summary | | vitest.config.* | npx vitest run --coverage | | pytest.ini / pyproject.toml pytest | pytest --cov=src --cov-report=json | | Cargo.toml | cargo llvm-cov --json | | pom.xml with JaCoCo | mvn test jacoco:report | | go.mod | go test -coverprofile=coverage.out ./... | ## Step 2: Analyze Coverage Report 1. Run the coverage command 2. Parse the output (JSON summary or terminal output) 3. List files below 80% coverage, sorted worst-first 4. For each under-covered file, identify: - Untested functions or methods - Missing branch coverage (if/else, switch, error paths) - Dead code that inflates the denominator ## Step 3: Generate Missing Tests For each under-covered file, generate tests following this priority: 1. Happy path : Core functionality with valid inputs 2. Error handling : Invalid inputs, missing data, network failures 3. Edge cases : Empty arrays, null/undefined, boundary values (0, -1, MAX_INT) 4. Branch coverage : Each if/else, switch case, ternary ### Test Generation Rules - Place tests adjacent to source: foo.ts → foo.test.ts (or project convention) - Use existing test patterns from the project (import style, assertion library, mocking approach) - Mock external dependencies (database, APIs, file system) - Each test should be independent : no shared mutable state between tests - Name tests descriptively: test_create_user_with_duplicate_email_returns_409 ## Step 4: Verify 1. Run the full test suite : all tests must pass 2. Re-run coverage : verify improvement 3. If still below 80%, repeat Step 3 for remaining gaps ## Step 5: Report Show before/after comparison: `` Coverage Report ────────────────────────────── File Before After src/services/auth.ts 45% 88% src/utils/validation.ts 32% 82% ────────────────────────────── Overall: 67% 84% PASS: `` ## Focus Areas - Functions with complex branching (high cyclomatic complexity) - Error handlers and catch blocks - Utility functions used across the codebase - API endpoint handlers (request → response flow) - Edge cases: null, undefined, empty string, empty array, zero, negative numbers