test-automation-expert

Test Automation Expert Comprehensive testing guidance from unit to E2E. Designs test strategies, implements automation, and optimizes coverage for sustainable quality. When to Use Use for: - Designing test strategy for new projects - Setting up testing frameworks (Jest, Vitest, Playwright, Cypress, pytest) - Writing effective unit, integration, and E2E tests - Optimizing test coverage and eliminating gaps - Debugging flaky tests - CI/CD test pipeline configuration - Test-Driven Development (TDD) guidance - Mocking strategies and test fixtures Do NOT use for: - Manual QA test case writing - th…

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Important: agents should read /llm.txt, /llms.txt, or /.well-known/skills.json to discover the public Skillopedia API.

: 'identity-obj-proxy'\n },\n collectCoverageFrom: [\n 'src/**/*.{ts,tsx}',\n '!src/**/*.d.ts'\n ],\n coverageThreshold: {\n global: {\n branches: 75,\n functions: 80,\n lines: 80\n }\n }\n};\n```\n\n**Vitest (vitest.config.ts):**\n```typescript\nimport { defineConfig } from 'vitest/config';\nimport react from '@vitejs/plugin-react';\n\nexport default defineConfig({\n plugins: [react()],\n test: {\n environment: 'jsdom',\n setupFiles: ['./vitest.setup.ts'],\n globals: true,\n coverage: {\n provider: 'v8',\n reporter: ['text', 'json', 'html'],\n exclude: ['node_modules/', 'test/']\n }\n },\n resolve: {\n alias: {\n '@': '/src'\n }\n }\n});\n```\n\n## E2E Testing Frameworks\n\n### Comparison Matrix\n\n| Feature | Playwright | Cypress | Selenium |\n|---------|------------|---------|----------|\n| **Browsers** | All major | Chrome, FF, Edge | All major |\n| **Speed** | Fast | Fast | Slow |\n| **Parallel** | Native | Paid feature | External |\n| **Mobile** | Emulation | Limited | Appium |\n| **Network Mock** | Built-in | Built-in | Manual |\n| **Auto-wait** | Excellent | Good | Manual |\n| **Debugging** | Inspector, trace | Time travel | Limited |\n| **Language** | JS/TS/Python/C#/.NET | JS/TS only | Many |\n| **CI/CD** | Excellent | Good | Complex |\n| **Learning Curve** | Low | Low | High |\n| **Open Source** | Yes | Yes (core) | Yes |\n\n### When to Choose Each\n\n**Choose Playwright when:**\n- Cross-browser testing is critical\n- Need WebKit/Safari testing\n- API testing alongside E2E\n- Multiple language support needed\n- Complex scenarios (multiple tabs, auth)\n\n**Choose Cypress when:**\n- Developer experience is priority\n- React/Vue/Angular component testing\n- Team new to E2E testing\n- Single browser is acceptable\n- Real-time debugging needed\n\n**Choose Selenium when:**\n- Legacy infrastructure exists\n- Need language flexibility\n- Complex enterprise requirements\n- Grid-based parallel execution\n\n### Configuration Examples\n\n**Playwright (playwright.config.ts):**\n```typescript\nimport { defineConfig, devices } from '@playwright/test';\n\nexport default defineConfig({\n testDir: './e2e',\n fullyParallel: true,\n forbidOnly: !!process.env.CI,\n retries: process.env.CI ? 2 : 0,\n workers: process.env.CI ? 2 : undefined,\n reporter: [\n ['html'],\n ['junit', { outputFile: 'results.xml' }]\n ],\n use: {\n baseURL: 'http://localhost:3000',\n trace: 'on-first-retry',\n screenshot: 'only-on-failure'\n },\n projects: [\n {\n name: 'chromium',\n use: { ...devices['Desktop Chrome'] }\n },\n {\n name: 'firefox',\n use: { ...devices['Desktop Firefox'] }\n },\n {\n name: 'webkit',\n use: { ...devices['Desktop Safari'] }\n },\n {\n name: 'mobile-chrome',\n use: { ...devices['Pixel 5'] }\n }\n ],\n webServer: {\n command: 'npm run dev',\n url: 'http://localhost:3000',\n reuseExistingServer: !process.env.CI\n }\n});\n```\n\n**Cypress (cypress.config.ts):**\n```typescript\nimport { defineConfig } from 'cypress';\n\nexport default defineConfig({\n e2e: {\n baseUrl: 'http://localhost:3000',\n viewportWidth: 1280,\n viewportHeight: 720,\n video: false,\n screenshotOnRunFailure: true,\n retries: {\n runMode: 2,\n openMode: 0\n },\n setupNodeEvents(on, config) {\n // Task plugins\n on('task', {\n seedDatabase(data) {\n return db.seed(data);\n }\n });\n }\n },\n component: {\n devServer: {\n framework: 'react',\n bundler: 'vite'\n }\n }\n});\n```\n\n## Python Testing Frameworks\n\n### Comparison\n\n| Feature | pytest | unittest | nose2 |\n|---------|--------|----------|-------|\n| **Syntax** | Simple | Verbose | Simple |\n| **Fixtures** | Powerful | setUp/tearDown | Basic |\n| **Plugins** | 800+ | Limited | Some |\n| **Parametrize** | Built-in | SubTest | Plugin |\n| **Assertions** | Plain assert | self.assertEqual | Plain |\n| **Discovery** | Automatic | Manual | Automatic |\n| **Markers** | Flexible | Limited | Limited |\n| **Parallel** | pytest-xdist | No | Limited |\n\n### pytest Configuration\n\n**pyproject.toml:**\n```toml\n[tool.pytest.ini_options]\ntestpaths = [\"tests\"]\npython_files = [\"test_*.py\", \"*_test.py\"]\npython_functions = [\"test_*\"]\naddopts = [\n \"-v\",\n \"--strict-markers\",\n \"--cov=src\",\n \"--cov-report=term-missing\",\n \"--cov-report=html\",\n \"--cov-fail-under=80\"\n]\nmarkers = [\n \"slow: marks tests as slow\",\n \"integration: marks tests as integration tests\",\n \"e2e: marks tests as end-to-end tests\"\n]\nfilterwarnings = [\n \"error\",\n \"ignore::DeprecationWarning\"\n]\n\n[tool.coverage.run]\nbranch = true\nsource = [\"src\"]\nomit = [\"tests/*\", \"**/__init__.py\"]\n\n[tool.coverage.report]\nexclude_lines = [\n \"pragma: no cover\",\n \"if TYPE_CHECKING:\",\n \"raise NotImplementedError\"\n]\n```\n\n**conftest.py:**\n```python\nimport pytest\nfrom sqlalchemy import create_engine\nfrom sqlalchemy.orm import sessionmaker\n\[email protected](scope=\"session\")\ndef engine():\n return create_engine(\"sqlite:///:memory:\")\n\[email protected](scope=\"function\")\ndef db_session(engine):\n Session = sessionmaker(bind=engine)\n session = Session()\n yield session\n session.rollback()\n session.close()\n\[email protected]\ndef client(app):\n return app.test_client()\n\[email protected]\ndef auth_headers(client):\n response = client.post('/login', json={\n 'username': 'test',\n 'password': 'test123'\n })\n token = response.json['token']\n return {'Authorization': f'Bearer {token}'}\n```\n\n## Component Testing\n\n### React Testing Library vs Enzyme\n\n| Feature | React Testing Library | Enzyme |\n|---------|----------------------|--------|\n| **Philosophy** | User behavior | Implementation |\n| **Queries** | Accessibility-first | Component internals |\n| **Shallow** | Not supported | Supported |\n| **Maintained** | Active | Limited |\n| **React 18** | Full support | Partial |\n| **Learning** | Moderate | Easy |\n\n**React Testing Library (Recommended):**\n```javascript\nimport { render, screen, waitFor } from '@testing-library/react';\nimport userEvent from '@testing-library/user-event';\n\ntest('submits form with user data', async () => {\n const user = userEvent.setup();\n const onSubmit = jest.fn();\n\n render(\u003cLoginForm onSubmit={onSubmit} />);\n\n await user.type(screen.getByLabelText(/email/i), '[email protected]');\n await user.type(screen.getByLabelText(/password/i), 'password123');\n await user.click(screen.getByRole('button', { name: /sign in/i }));\n\n await waitFor(() => {\n expect(onSubmit).toHaveBeenCalledWith({\n email: '[email protected]',\n password: 'password123'\n });\n });\n});\n```\n\n## API Testing\n\n### Framework Options\n\n| Tool | Language | Best For |\n|------|----------|----------|\n| Supertest | JS/TS | Express/Node |\n| Playwright Request | JS/TS | With E2E |\n| pytest + requests | Python | Flask/Django |\n| REST Assured | Java | Spring |\n| Postman/Newman | Any | CI/CD |\n\n**Supertest Example:**\n```javascript\nimport request from 'supertest';\nimport app from '../src/app';\n\ndescribe('Users API', () => {\n it('GET /users returns list', async () => {\n const response = await request(app)\n .get('/api/users')\n .set('Authorization', `Bearer ${token}`)\n .expect('Content-Type', /json/)\n .expect(200);\n\n expect(response.body).toHaveLength(10);\n expect(response.body[0]).toHaveProperty('id');\n });\n});\n```\n\n## Decision Matrix\n\n### Quick Selection Guide\n\n```\nNeed to test...\n│\n├── Unit/Business Logic\n│ ├── JavaScript/TypeScript\n│ │ ├── Using Vite → Vitest\n│ │ ├── Existing Jest → Keep Jest\n│ │ └── New project → Vitest\n│ └── Python → pytest\n│\n├── React Components\n│ ├── User behavior → React Testing Library\n│ └── With stories → Storybook + Chromatic\n│\n├── API Endpoints\n│ ├── Node.js → Supertest\n│ ├── With E2E → Playwright API\n│ └── Python → pytest + requests\n│\n└── E2E/Browser\n ├── Cross-browser critical → Playwright\n ├── Developer experience → Cypress\n └── Legacy/Enterprise → Selenium\n```\n","content_type":"text/markdown; charset=utf-8","language":"markdown","size":9669,"content_sha256":"ce5bbd87e5d7b15d031f7762cf65f0d56e14afb5a7bff55145ecb41815785543"},{"filename":"references/test-strategy.md","content":"# Test Strategy Framework\n\nA comprehensive guide to building effective test strategies for modern applications.\n\n## Test Strategy Document Template\n\n### 1. Scope Definition\n\n**In Scope:**\n- [ ] Unit tests for business logic\n- [ ] Integration tests for API contracts\n- [ ] E2E tests for critical user journeys\n- [ ] Component tests for UI elements\n- [ ] Accessibility testing\n- [ ] Visual regression testing\n\n**Out of Scope:**\n- [ ] Performance/load testing (separate strategy)\n- [ ] Security testing (separate strategy)\n- [ ] Manual exploratory testing\n\n### 2. Test Pyramid Implementation\n\n```\nTarget Distribution:\n━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━\nE2E: ████████░░░░░░░░░░░░░░░░░░░░░░ 10%\nIntegration: ████████████████░░░░░░░░░░░░░░ 20%\nUnit: ████████████████████████████████ 70%\n━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━\n```\n\n### 3. Critical Path Identification\n\n**Tier 1 - Must Never Break (100% coverage):**\n- User authentication flow\n- Payment/checkout process\n- Core data mutations\n- Security-critical operations\n\n**Tier 2 - Important (90% coverage):**\n- User profile management\n- Search and filtering\n- Navigation flows\n- Form submissions\n\n**Tier 3 - Nice to Have (70% coverage):**\n- Edge cases in UI\n- Administrative features\n- Logging and analytics\n\n### 4. Test Data Strategy\n\n**Approaches:**\n1. **Factory Pattern** - Generate test data programmatically\n2. **Fixtures** - Static test data files\n3. **Seeding** - Database seeding scripts\n4. **Mocking** - API response mocks\n\n**Data Isolation:**\n```javascript\n// Each test gets fresh data\nbeforeEach(async () => {\n await db.truncate(['users', 'orders']);\n await seedTestData();\n});\n```\n\n### 5. Environment Strategy\n\n| Environment | Purpose | Data | Speed |\n|-------------|---------|------|-------|\n| Local | Development | Mocked/Seeded | Fast |\n| CI | Automation | Seeded | Medium |\n| Staging | Pre-prod validation | Sanitized prod | Slow |\n| Production | Smoke tests only | Real | N/A |\n\n### 6. Ownership Model\n\n| Test Type | Owner | Review |\n|-----------|-------|--------|\n| Unit tests | Feature developer | Code review |\n| Integration tests | Feature team | Tech lead |\n| E2E tests | QA/Platform team | QA lead |\n| Performance tests | Platform team | SRE |\n\n## Risk-Based Testing\n\n### Risk Assessment Matrix\n\n```\nImpact\n ↑\n │ ┌─────────┬─────────┐\nH │ │ MEDIUM │ HIGH │ ← Comprehensive testing\n │ │ Priority│ Priority│\n │ ├─────────┼─────────┤\nM │ │ LOW │ MEDIUM │ ← Standard testing\n │ │ Priority│ Priority│\n │ ├─────────┼─────────┤\nL │ │ MINIMAL│ LOW │ ← Basic coverage\n │ │ Priority│ Priority│\n └──┴─────────┴─────────┴──→\n Low High Probability\n```\n\n### Coverage by Risk Level\n\n| Risk | Min Coverage | Test Types |\n|------|-------------|------------|\n| High | 95% | Unit + Integration + E2E |\n| Medium | 80% | Unit + Integration |\n| Low | 60% | Unit |\n| Minimal | 40% | Unit (happy path) |\n\n## Testing Quadrants\n\n```\n Business-Facing\n ↑\n Q2 │ │ Q3\nFunctional │ Exploratory\n Tests │ Testing\n │\n──────────────┼──────────────→ Manual\n │\n Q1 │ │ Q4\n Unit │ Performance\n Tests │ Security\n │\n Technology-Facing\n ↓\n Automated\n```\n\n**Q1 (Technology/Automated):** Unit tests, component tests\n**Q2 (Business/Automated):** Functional tests, API tests\n**Q3 (Business/Manual):** Exploratory testing, usability\n**Q4 (Technology/Tools):** Performance, security, load\n\n## Test Maintenance Strategy\n\n### Keeping Tests Healthy\n\n1. **Regular Review Cycles**\n - Weekly: Flaky test triage\n - Monthly: Coverage gaps analysis\n - Quarterly: Strategy review\n\n2. **Test Debt Tracking**\n ```\n # In test file headers\n // @tech-debt: Needs refactor when API v2 ships\n // @flaky: Intermittent timeout - tracking in JIRA-123\n // @skip-reason: Blocked by feature flag removal\n ```\n\n3. **Deletion Criteria**\n - Test for removed feature\n - Duplicate coverage\n - Permanently flaky with no fix path\n - Testing implementation details\n\n### Metrics to Track\n\n| Metric | Target | Alert |\n|--------|--------|-------|\n| Test pass rate | >99% | <98% |\n| Flaky test rate | <1% | >2% |\n| Coverage trend | Stable/Up | -5% |\n| Test run time | <10min | >15min |\n| Time to fix failed test | <4hrs | >24hrs |\n\n## Test Documentation Standards\n\n### Test Naming Convention\n\n```javascript\n// Pattern: should_[expected]_when_[condition]\nit('should_return_user_when_id_exists', () => {});\nit('should_throw_error_when_id_invalid', () => {});\n\n// Or: describe behavior\ndescribe('UserService', () => {\n describe('getUser', () => {\n it('returns user for valid ID', () => {});\n it('throws NotFoundError for unknown ID', () => {});\n });\n});\n```\n\n### Test File Organization\n\n```\nsrc/\n├── components/\n│ ├── Button/\n│ │ ├── Button.tsx\n│ │ ├── Button.test.tsx # Unit tests\n│ │ └── Button.stories.tsx # Visual tests\n├── services/\n│ ├── user.ts\n│ └── user.test.ts\ntests/\n├── integration/\n│ ├── api/\n│ │ └── users.test.ts\n│ └── setup.ts\n├── e2e/\n│ ├── checkout.spec.ts\n│ └── auth.spec.ts\n└── fixtures/\n └── users.json\n```\n\n## Continuous Improvement\n\n### Retrospective Questions\n\n1. What tests caught real bugs this sprint?\n2. What bugs escaped to production - why no test?\n3. Which tests are frequently skipped/ignored?\n4. What's the test run time trend?\n5. Are developers writing tests first (TDD) or after?\n\n### Improvement Actions\n\n| Issue | Action |\n|-------|--------|\n| Low coverage | Pair on test writing |\n| Slow tests | Parallelize, mock more |\n| Flaky tests | Dedicated fix sprints |\n| Missing E2E | Map critical paths |\n| Test debt | Budget 10% for maintenance |\n","content_type":"text/markdown; charset=utf-8","language":"markdown","size":6634,"content_sha256":"8a50280ef5e2ff4eaee5da109c9f001460f7de1f9d734d1398bbc1b1f3dcc78a"}],"content_json":{"type":"doc","content":[{"type":"heading","attrs":{"level":1},"content":[{"text":"Test Automation Expert","type":"text"}]},{"type":"paragraph","content":[{"text":"Comprehensive testing guidance from unit to E2E. Designs test strategies, implements automation, and optimizes coverage for sustainable quality.","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"When to Use","type":"text"}]},{"type":"paragraph","content":[{"text":"Use for:","type":"text","marks":[{"type":"strong"}]}]},{"type":"bullet_list","content":[{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Designing test strategy for new projects","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Setting up testing frameworks (Jest, Vitest, Playwright, Cypress, pytest)","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Writing effective unit, integration, and E2E tests","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Optimizing test coverage and eliminating gaps","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Debugging flaky tests","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"CI/CD test pipeline configuration","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Test-Driven Development (TDD) guidance","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Mocking strategies and test fixtures","type":"text"}]}]}]},{"type":"paragraph","content":[{"text":"Do NOT use for:","type":"text","marks":[{"type":"strong"}]}]},{"type":"bullet_list","content":[{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Manual QA test case writing - this is automation-focused","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Load/performance testing - use performance-engineer skill","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Security testing - use security-auditor skill","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"API contract testing only - use backend-architect for API design","type":"text"}]}]}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"Test Pyramid Philosophy","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":""},"content":[{"text":" /\\\n / \\ E2E Tests (10%)\n /----\\ - Critical user journeys\n / \\ - Cross-browser validation\n /--------\\\n / \\ Integration Tests (20%)\n / \\ - API contracts\n /--------------\\- Component interactions\n / \\\n/------------------\\ Unit Tests (70%)\n - Fast, isolated, deterministic\n - Business logic validation","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Distribution Guidelines","type":"text"}]},{"type":"table","attrs":{"layout":null},"content":[{"type":"tr","content":[{"type":"th","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Test Type","type":"text"}]}]},{"type":"th","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Percentage","type":"text"}]}]},{"type":"th","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Execution 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validation","type":"text"}]}]}]},{"type":"tr","content":[{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Integration","type":"text"}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"20%","type":"text"}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"\u003c 1s each","type":"text"}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Component 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Selection","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"JavaScript/TypeScript","type":"text"}]},{"type":"table","attrs":{"layout":null},"content":[{"type":"tr","content":[{"type":"th","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Framework","type":"text"}]}]},{"type":"th","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Best For","type":"text"}]}]},{"type":"th","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Speed","type":"text"}]}]},{"type":"th","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Config 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ESM","type":"text"}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Fastest","type":"text"}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Low","type":"text"}]}]}]},{"type":"tr","content":[{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Jest","type":"text","marks":[{"type":"strong"}]}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"React, established projects","type":"text"}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Fast","type":"text"}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Medium","type":"text"}]}]}]},{"type":"tr","content":[{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"Playwright","type":"text","marks":[{"type":"strong"}]}]}]},{"type":"td","attrs":{"colspan":1,"rowspan":1,"colwidth":null,"alignment":""},"content":[{"type":"paragraph","content":[{"text":"E2E, 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Tree: Framework Selection","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":""},"content":[{"text":"New project?\n├── Yes → Using Vite?\n│ ├── Yes → Vitest\n│ └── No → Jest or Vitest (both work)\n└── No → What exists?\n ├── Jest → Keep Jest (migration cost rarely worth it)\n ├── Mocha → Consider migration to Vitest\n └── Nothing → Vitest (modern default)\n\nNeed E2E?\n├── Cross-browser critical → Playwright\n├── Developer experience priority → Cypress\n└── Both → Playwright (more flexible)","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"Unit Testing Patterns","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Good Unit Test Anatomy","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"describe('UserService', () => {\n describe('validateEmail', () => {\n // Arrange-Act-Assert pattern\n it('should accept valid email formats', () => {\n // Arrange\n const validEmails = ['[email protected]', '[email protected]'];\n\n // Act & Assert\n validEmails.forEach(email => {\n expect(validateEmail(email)).toBe(true);\n });\n });\n\n it('should reject invalid email formats', () => {\n // Arrange\n const invalidEmails = ['invalid', '@missing.com', 'no@tld'];\n\n // Act & Assert\n invalidEmails.forEach(email => {\n expect(validateEmail(email)).toBe(false);\n });\n });\n\n // Edge cases explicitly tested\n it('should handle empty string', () => {\n expect(validateEmail('')).toBe(false);\n });\n\n it('should handle null/undefined', () => {\n expect(validateEmail(null)).toBe(false);\n expect(validateEmail(undefined)).toBe(false);\n });\n });\n});","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Mocking Strategies","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"// ✅ Good: Mock at boundaries\njest.mock('../services/api', () => ({\n fetchUser: jest.fn()\n}));\n\n// ✅ Good: Explicit mock setup per test\nbeforeEach(() => {\n fetchUser.mockReset();\n});\n\nit('handles user not found', async () => {\n fetchUser.mockRejectedValue(new NotFoundError());\n await expect(getUser(123)).rejects.toThrow('User not found');\n});\n\n// ❌ Bad: Mocking implementation details\njest.mock('../utils/internal-helper'); // Don't mock internals","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Test Isolation Checklist","type":"text"}]},{"type":"checkbox_list","attrs":{"id":null},"content":[{"type":"checkbox_item","attrs":{"checked":false},"content":[{"type":"paragraph","content":[{"text":"Each test can run independently","type":"text"}]}]},{"type":"checkbox_item","attrs":{"checked":false},"content":[{"type":"paragraph","content":[{"text":"No shared mutable state between tests","type":"text"}]}]},{"type":"checkbox_item","attrs":{"checked":false},"content":[{"type":"paragraph","content":[{"text":"Database/API state reset between tests","type":"text"}]}]},{"type":"checkbox_item","attrs":{"checked":false},"content":[{"type":"paragraph","content":[{"text":"No test order dependencies","type":"text"}]}]},{"type":"checkbox_item","attrs":{"checked":false},"content":[{"type":"paragraph","content":[{"text":"Parallel execution safe","type":"text"}]}]}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"Integration Testing Patterns","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"API Integration Test","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"describe('POST /api/users', () => {\n let app;\n let db;\n\n beforeAll(async () => {\n db = await createTestDatabase();\n app = createApp({ db });\n });\n\n afterAll(async () => {\n await db.close();\n });\n\n beforeEach(async () => {\n await db.clear();\n });\n\n it('creates user with valid data', async () => {\n const response = await request(app)\n .post('/api/users')\n .send({ name: 'Test', email: '[email protected]' })\n .expect(201);\n\n expect(response.body).toMatchObject({\n id: expect.any(String),\n name: 'Test',\n email: '[email protected]'\n });\n\n // Verify side effects\n const dbUser = await db.users.findById(response.body.id);\n expect(dbUser).toBeDefined();\n });\n\n it('rejects duplicate email', async () => {\n await db.users.create({ name: 'Existing', email: '[email protected]' });\n\n await request(app)\n .post('/api/users')\n .send({ name: 'New', email: '[email protected]' })\n .expect(409);\n });\n});","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Component Integration (React)","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"import { render, screen, waitFor } from '@testing-library/react';\nimport userEvent from '@testing-library/user-event';\nimport { UserProfile } from './UserProfile';\nimport { UserProvider } from '../context/UserContext';\n\ndescribe('UserProfile integration', () => {\n it('loads and displays user data', async () => {\n render(\n \u003cUserProvider>\n \u003cUserProfile userId=\"123\" />\n \u003c/UserProvider>\n );\n\n // Verify loading state\n expect(screen.getByRole('progressbar')).toBeInTheDocument();\n\n // Wait for data\n await waitFor(() => {\n expect(screen.getByText('John Doe')).toBeInTheDocument();\n });\n\n // Verify loaded state\n expect(screen.queryByRole('progressbar')).not.toBeInTheDocument();\n });\n});","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"E2E Testing Patterns","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Playwright Best Practices","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"import { test, expect } from '@playwright/test';\n\ntest.describe('Checkout Flow', () => {\n test.beforeEach(async ({ page }) => {\n // Seed test data via API\n await page.request.post('/api/test/seed', {\n data: { scenario: 'checkout-ready' }\n });\n });\n\n test('complete purchase with credit card', async ({ page }) => {\n await page.goto('/cart');\n\n // Use accessible selectors\n await page.getByRole('button', { name: 'Proceed to checkout' }).click();\n\n // Fill payment form\n await page.getByLabel('Card number').fill('4242424242424242');\n await page.getByLabel('Expiry').fill('12/25');\n await page.getByLabel('CVC').fill('123');\n\n // Complete purchase\n await page.getByRole('button', { name: 'Pay now' }).click();\n\n // Verify success\n await expect(page.getByRole('heading', { name: 'Order confirmed' })).toBeVisible();\n await expect(page.getByText(/Order #\\d+/)).toBeVisible();\n });\n\n test('shows error for declined card', async ({ page }) => {\n await page.goto('/checkout');\n\n // Use test card that triggers decline\n await page.getByLabel('Card number').fill('4000000000000002');\n await page.getByLabel('Expiry').fill('12/25');\n await page.getByLabel('CVC').fill('123');\n\n await page.getByRole('button', { name: 'Pay now' }).click();\n\n await expect(page.getByRole('alert')).toContainText('Card declined');\n });\n});","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Flaky Test Detection & Prevention","type":"text"}]},{"type":"paragraph","content":[{"text":"Common Causes:","type":"text","marks":[{"type":"strong"}]}]},{"type":"ordered_list","attrs":{"order":1,"listStyle":"number"},"content":[{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Race conditions in async operations","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Time-dependent tests","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Shared state between tests","type":"text"}]}]},{"type":"list_item","content":[{"type":"paragraph","content":[{"text":"Network 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Configuration","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"// vitest.config.js\nexport default defineConfig({\n test: {\n coverage: {\n provider: 'v8',\n reporter: ['text', 'json', 'html'],\n exclude: [\n 'node_modules/',\n 'test/',\n '**/*.d.ts',\n '**/*.config.*',\n '**/index.ts', // barrel files\n ],\n thresholds: {\n branches: 75,\n functions: 80,\n lines: 80,\n statements: 80\n }\n }\n }\n});","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Finding Coverage Gaps","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"bash"},"content":[{"text":"# Generate detailed coverage report\nnpx vitest run --coverage\n\n# Find untested files\nnpx vitest run --coverage --reporter=json | jq '.coverageMap | to_entries | map(select(.value.s | values | any(. == 0))) | .[].key'","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"CI/CD Integration","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"GitHub Actions","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"yaml"},"content":[{"text":"name: Tests\non: [push, pull_request]\n\njobs:\n unit-tests:\n runs-on: ubuntu-latest\n steps:\n - uses: actions/checkout@v4\n - uses: actions/setup-node@v4\n with:\n node-version: '20'\n cache: 'npm'\n - run: npm ci\n - run: npm test -- --coverage\n - uses: codecov/codecov-action@v4\n\n e2e-tests:\n runs-on: ubuntu-latest\n steps:\n - uses: actions/checkout@v4\n - uses: actions/setup-node@v4\n - run: npm ci\n - run: npx playwright install --with-deps\n - run: npm run test:e2e\n - uses: actions/upload-artifact@v4\n if: failure()\n with:\n name: playwright-report\n path: playwright-report/","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Test Parallelization","type":"text"}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"// vitest.config.js - parallel by default\nexport default defineConfig({\n test: {\n pool: 'threads',\n poolOptions: {\n threads: {\n singleThread: false\n }\n }\n }\n});\n\n// playwright.config.js\nexport default defineConfig({\n workers: process.env.CI ? 2 : undefined,\n fullyParallel: true\n});","type":"text"}]},{"type":"heading","attrs":{"level":2},"content":[{"text":"Anti-Patterns","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Anti-Pattern: Testing Implementation Details","type":"text"}]},{"type":"paragraph","content":[{"text":"What it looks like:","type":"text","marks":[{"type":"strong"}]}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"// ❌ Testing internal state\nexpect(component.state.isLoading).toBe(true);\n\n// ❌ Testing private methods\nexpect(service._calculateHash()).toBe('abc123');","type":"text"}]},{"type":"paragraph","content":[{"text":"Why wrong:","type":"text","marks":[{"type":"strong"}]},{"text":" Couples tests to implementation, breaks on refactors","type":"text"}]},{"type":"paragraph","content":[{"text":"Instead:","type":"text","marks":[{"type":"strong"}]}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"// ✅ Test observable behavior\nexpect(screen.getByRole('progressbar')).toBeInTheDocument();\n\n// ✅ Test public interface\nexpect(service.getHash()).toBe('abc123');","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Anti-Pattern: Over-Mocking","type":"text"}]},{"type":"paragraph","content":[{"text":"What it looks like:","type":"text","marks":[{"type":"strong"}]}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"// ❌ Mocking everything\njest.mock('../utils/format');\njest.mock('../utils/validate');\njest.mock('../utils/transform');","type":"text"}]},{"type":"paragraph","content":[{"text":"Why wrong:","type":"text","marks":[{"type":"strong"}]},{"text":" Tests pass even when real code is broken","type":"text"}]},{"type":"paragraph","content":[{"text":"Instead:","type":"text","marks":[{"type":"strong"}]},{"text":" Mock only at system boundaries (APIs, databases, external services)","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Anti-Pattern: Flaky Acceptance","type":"text"}]},{"type":"paragraph","content":[{"text":"What it looks like:","type":"text","marks":[{"type":"strong"}]},{"text":" \"That test is just flaky, skip it\"","type":"text"}]},{"type":"paragraph","content":[{"text":"Why wrong:","type":"text","marks":[{"type":"strong"}]},{"text":" Flaky tests indicate real problems (race conditions, timing issues)","type":"text"}]},{"type":"paragraph","content":[{"text":"Instead:","type":"text","marks":[{"type":"strong"}]},{"text":" Fix the flakiness or quarantine while fixing","type":"text"}]},{"type":"heading","attrs":{"level":3},"content":[{"text":"Anti-Pattern: Coverage Theater","type":"text"}]},{"type":"paragraph","content":[{"text":"What it looks like:","type":"text","marks":[{"type":"strong"}]}]},{"type":"code_block","attrs":{"wrap":false,"language":"javascript"},"content":[{"text":"// ❌ Testing for coverage, not behavior\nit('covers the function', () => {\n myFunction();\n // No assertions!\n});","type":"text"}]},{"type":"paragraph","content":[{"text":"Why wrong:","type":"text","marks":[{"type":"strong"}]},{"text":" 100% coverage with 0% confidence","type":"text"}]},{"type":"paragraph","content":[{"text":"Instead:","type":"text","marks":[{"type":"strong"}]},{"text":" Every test should assert meaningful 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Important: agents should read /llm.txt, /llms.txt, or /.well-known/skills.json to discover the public Skillopedia API.