Test Automator Expert in creating and maintaining automated tests for various frameworks and languages. When This Skill Activates Activates when you: Ask to write tests Mention test automation Request test coverage improvement Need to set up testing framework Testing Pyramid /\ /E2E\ - Few, expensive, slow /------\ / Integration \ - Moderate number /--------------\ / Unit Tests \ - Many, cheap, fast /------------------\ Unit Testing Principles Test behavior, not implementation One assertion per test (generally) Arrange-Act-Assert pattern Descriptive test names Example (Jest) describe ( 'UserService' , ( ) => { describe ( 'createUser' , ( ) => { it ( 'should create a user with valid data' , async ( ) => { // Arrange const userData = { name : 'John Doe' , email : 'john@example.com' } ; // Act const user = await userService . create ( userData ) ; // Assert expect ( user . id ) . toBeDefined ( ) ; expect ( user . email ) . toBe ( userData . email ) ; } ) ; it ( 'should throw error for invalid email' , async ( ) => { // Arrange const userData = { email : 'invalid' } ; // Act & Assert await expect ( userService . create ( userData ) ) . rejects . toThrow ( 'Invalid email' ) ; } ) ; } ) ; } ) ; Integration Testing Principles Test component interactions Use test doubles for external services Clean up test data Run in isolation Example (Supertest) describe ( 'POST /api/users' , ( ) => { it ( 'should create a user' , async ( ) => { const response = await request ( app ) . post ( '/api/users' ) . send ( { name : 'John Doe' , email : 'john@example.com' } ) . expect ( 201 ) . expect ( ( res ) => { expect ( res . body . id ) . toBeDefined ( ) ; expect ( res . body . email ) . toBe ( 'john@example.com' ) ; } ) ; } ) ; } ) ; E2E Testing Principles Test critical user flows Use realistic test data Handle async operations properly Clean up after tests Example (Playwright) test ( 'user can login' , async ( { page } ) => { await page . goto ( '/login' ) ; await page . fill ( '[name="email"]' , 'user@example.com' ) ; await page . fill ( '[name="password"]' , 'password123' ) ; await page . click ( 'button[type="submit"]' ) ; await expect ( page ) . toHaveURL ( '/dashboard' ) ; await expect ( page . locator ( 'h1' ) ) . toContainText ( 'Welcome' ) ; } ) ; Test Coverage Coverage Goals Type Target Lines

80% Branches 75% Functions 80% Statements 80% Coverage Reports

Jest

npm test -- --coverage

Python (pytest-cov)

pytest --cov = src --cov-report = html

Go

go test -coverprofile = coverage.out go tool cover -html = coverage.out Testing Best Practices DO's Write tests before fixing bugs (TDD) Test edge cases Keep tests independent Use descriptive test names Mock external dependencies Clean up test data DON'Ts Don't test implementation details Don't write brittle tests Don't skip tests without a reason Don't commit commented-out tests Don't test third-party libraries Test Naming Conventions // Good: Describes what is being tested it ( 'should reject invalid email addresses' ) // Good: Describes the scenario and outcome it ( 'returns 401 when user provides invalid credentials' ) // Bad: Vague it ( 'works correctly' ) Common Testing Frameworks Language Framework Command TypeScript/JS Jest, Vitest npm test Python pytest pytest Go testing go test Java JUnit mvn test Rust built-in cargo test Scripts Generate test boilerplate: python scripts/generate_test.py < filename

Check test coverage: python scripts/coverage_report.py References references/best-practices.md - Testing best practices references/examples/ - Framework-specific examples references/mocking.md - Mocking guidelines