JackSmack1971/.agents/skills/playwright-best-practices-skill/playwright-best-practices

description: Writes Playwright end-to-end tests with best-practice selectors and assertions.

Summary

• Covers 50+ testing patterns including E2E, component, API, GraphQL, visual regression, accessibility, security, mobile, and Electron app testing
• Includes activity-based lookup tables for writing new tests, debugging failures, fixing flaky tests, and infrastructure setup
• Provides decision trees for test type selection, architecture patterns (POM vs fixtures), framework-specific guidance (React, Angular, Vue, Next.js), and error scenario handling
• Addresses advanced topics: multi-user collaboration, WebSocket/real-time testing, OAuth/SSO mocking, third-party service integration, performance budgeting, and console error monitoring

---

description: Writes Playwright end-to-end tests with best-practice selectors and assertions.

SKILL.md

Playwright Best Practices

This skill provides comprehensive guidance for all aspects of Playwright test development, from writing new tests to debugging and maintaining existing test suites.

Activity-Based Reference Guide

Consult these references based on what you're doing:

Writing New Tests

When to use: Creating new test files, writing test cases, implementing test scenarios

| Activity | Reference Files | | --- | --- | | Writing E2E tests | test-suite-structure.md, locators.md, assertions-waiting.md | | Writing component tests | component-testing.md, test-suite-structure.md | | Writing API tests | api-testing.md, test-suite-structure.md | | Writing GraphQL tests | graphql-testing.md, api-testing.md | | Writing visual regression tests | visual-regression.md, canvas-webgl.md | | Structuring test code with POM | page-object-model.md, test-suite-structure.md | | Setting up test data/fixtures | fixtures-hooks.md, test-data.md | | Handling authentication | authentication.md, authentication-flows.md | | Testing date/time features | clock-mocking.md | | Testing file upload/download | file-operations.md, file-upload-download.md | | Testing forms/validation | forms-validation.md | | Testing drag and drop | drag-drop.md | | Testing accessibility | accessibility.md | | Testing security (XSS, CSRF) | security-testing.md | | Using test annotations | annotations.md | | Using test tags | test-tags.md | | Testing iframes | iframes.md | | Testing canvas/WebGL | canvas-webgl.md | | Internationalization (i18n) | i18n.md | | Testing Electron apps | electron.md | | Testing browser extensions | browser-extensions.md |

Mobile & Responsive Testing

When to use: Testing mobile devices, touch interactions, responsive layouts

| Activity | Reference Files | | --- | --- | | Device emulation | mobile-testing.md | | Touch gestures (swipe, tap) | mobile-testing.md | | Viewport/breakpoint testing | mobile-testing.md | | Mobile-specific UI | mobile-testing.md, locators.md |

Real-Time & Browser APIs

When to use: Testing WebSockets, geolocation, permissions, multi-tab flows

| Activity | Reference Files | | --- | --- | | WebSocket/real-time testing | websockets.md | | Geolocation mocking | browser-apis.md | | Permission handling | browser-apis.md | | Clipboard testing | browser-apis.md | | Camera/microphone mocking | browser-apis.md | | Multi-tab/popup flows | multi-context.md | | OAuth popup handling | third-party.md, multi-context.md |

Debugging & Troubleshooting

When to use: Test failures, element not found, timeouts, unexpected behavior

| Activity | Reference Files | | --- | --- | | Debugging test failures | debugging.md, assertions-waiting.md | | Fixing flaky tests | flaky-tests.md, debugging.md, assertions-waiting.md | | Debugging flaky parallel runs | flaky-tests.md, performance.md, fixtures-hooks.md | | Ensuring test isolation / avoiding state leak | flaky-tests.md, fixtures-hooks.md, performance.md | | Fixing selector issues | locators.md, debugging.md | | Investigating timeout issues | assertions-waiting.md, debugging.md | | Using trace viewer | debugging.md | | Debugging race conditions | flaky-tests.md, debugging.md, assertions-waiting.md | | Debugging console/JS errors | console-errors.md, debugging.md |

Error & Edge Case Testing

When to use: Testing error states, offline mode, network failures, validation

| Activity | Reference Files | | --- | --- | | Error boundary testing | error-testing.md | | Network failure simulation | error-testing.md, network-advanced.md | | Offline mode testing | error-testing.md, service-workers.md | | Service worker testing | service-workers.md | | Loading state testing | error-testing.md | | Form validation testing | error-testing.md |

Multi-User & Collaboration Testing

When to use: Testing features involving multiple users, roles, or real-time collaboration

| Activity | Reference Files | | --- | --- | | Multiple users in one test | multi-user.md | | Real-time collaboration | multi-user.md, websockets.md | | Role-based access testing | multi-user.md | | Concurrent action testing | multi-user.md |

Architecture Decisions

When to use: Choosing test patterns, deciding between approaches, planning test architecture

| Activity | Reference Files | | --- | --- | | POM vs fixtures decision | pom-vs-fixtures.md | | Test type selection | test-architecture.md | | Mock vs real services | when-to-mock.md | | Test suite structure | test-suite-structure.md |

Framework-Specific Testing

When to use: Testing React, Angular, Vue, or Next.js applications

| Activity | Reference Files | | --- | --- | | Testing React apps | react.md | | Testing Angular apps | angular.md | | Testing Vue/Nuxt apps | vue.md | | Testing Next.js apps | nextjs.md |

Refactoring & Maintenance

When to use: Improving existing tests, code review, reducing duplication

| Activity | Reference Files | | --- | --- | | Refactoring to Page Object Model | page-object-model.md, test-suite-structure.md | | Improving test organization | test-suite-structure.md, page-object-model.md | | Extracting common setup/teardown | fixtures-hooks.md | | Replacing brittle selectors | locators.md | | Removing explicit waits | assertions-waiting.md | | Creating test data factories | test-data.md | | Configuration setup | configuration.md |

Infrastructure & Configuration

When to use: Setting up projects, configuring CI/CD, optimizing performance

| Activity | Reference Files | | --- | --- | | Configuring Playwright project | configuration.md, projects-dependencies.md | | Setting up CI/CD pipelines | ci-cd.md, github-actions.md | | GitHub Actions setup | github-actions.md | | GitLab CI setup | gitlab.md | | Other CI providers | other-providers.md | | Docker/container setup | docker.md | | Global setup & teardown | global-setup.md | | Project dependencies | projects-dependencies.md | | Optimizing test performance | performance.md, test-suite-structure.md | | Configuring parallel execution | parallel-sharding.md, performance.md | | Isolating test data between workers | fixtures-hooks.md, performance.md | | Test coverage | test-coverage.md | | Test reporting/artifacts | reporting.md |

Advanced Patterns

When to use: Complex scenarios, API mocking, network interception

| Activity | Reference Files | | --- | --- | | Mocking API responses | test-suite-structure.md, network-advanced.md | | Network interception | network-advanced.md, assertions-waiting.md | | GraphQL mocking | network-advanced.md | | HAR recording/playback | network-advanced.md | | Custom fixtures | fixtures-hooks.md | | Advanced waiting strategies | assertions-waiting.md | | OAuth/SSO mocking | third-party.md, multi-context.md | | Payment gateway mocking | third-party.md | | Email/SMS verification mocking | third-party.md | | Failing on console errors | console-errors.md | | Security testing (XSS, CSRF) | security-testing.md | | Performance budgets & Web Vitals | performance-testing.md | | Lighthouse integration | performance-testing.md | | Test annotations (skip, fixme) | annotations.md | | Test tags (@smoke, @fast) | test-tags.md | | Test steps for reporting | annotations.md |

Quick Decision Tree

What are you doing?
│
├─ Writing a new test?
│  ├─ E2E test → core/test-suite-structure.md, core/locators.md, core/assertions-waiting.md
│  ├─ Component test → testing-patterns/component-testing.md
│  ├─ API test → testing-patterns/api-testing.md, core/test-suite-structure.md
│  ├─ GraphQL test → testing-patterns/graphql-testing.md
│  ├─ Visual regression → testing-patterns/visual-regression.md
│  ├─ Visual/canvas test → testing-patterns/canvas-webgl.md, core/test-suite-structure.md
│  ├─ Accessibility test → testing-patterns/accessibility.md
│  ├─ Mobile/responsive test → advanced/mobile-testing.md
│  ├─ i18n/locale test → testing-patterns/i18n.md
│  ├─ Electron app test → testing-patterns/electron.md
│  ├─ Browser extension test → testing-patterns/browser-extensions.md
│  ├─ Multi-user test → advanced/multi-user.md
│  ├─ Form validation test → testing-patterns/forms-validation.md
│  └─ Drag and drop test → testing-patterns/drag-drop.md
│
├─ Testing specific features?
│  ├─ File upload/download → testing-patterns/file-operations.md, testing-patterns/file-upload-download.md
│  ├─ Date/time dependent → advanced/clock-mocking.md
│  ├─ WebSocket/real-time → browser-apis/websockets.md
│  ├─ Geolocation/permissions → browser-apis/browser-apis.md
│  ├─ OAuth/SSO mocking → advanced/third-party.md, advanced/multi-context.md
│  ├─ Payments/email/SMS → advanced/third-party.md
│  ├─ iFrames → browser-apis/iframes.md
│  ├─ Canvas/WebGL/charts → testing-patterns/canvas-webgl.md
│  ├─ Service workers/PWA → browser-apis/service-workers.md
│  ├─ i18n/localization → testing-patterns/i18n.md
│  ├─ Security (XSS, CSRF) → testing-patterns/security-testing.md
│  └─ Performance/Web Vitals → testing-patterns/performance-testing.md
│
├─ Architecture decisions?
│  ├─ POM vs fixtures → architecture/pom-vs-fixtures.md
│  ├─ Test type selection → architecture/test-architecture.md
│  ├─ Mock vs real services → architecture/when-to-mock.md
│  └─ Test suite structure → core/test-suite-structure.md
│
├─ Framework-specific testing?
│  ├─ React app → frameworks/react.md
│  ├─ Angular app → frameworks/angular.md
│  ├─ Vue/Nuxt app → frameworks/vue.md
│  └─ Next.js app → frameworks/nextjs.md
│
├─ Authentication testing?
│  ├─ Basic auth patterns → advanced/authentication.md
│  └─ Complex flows (MFA, reset) → advanced/authentication-flows.md
│
├─ Test is failing/flaky?
│  ├─ Flaky test investigation → debugging/flaky-tests.md
│  ├─ Element not found → core/locators.md, debugging/debugging.md
│  ├─ Timeout issues → core/assertions-waiting.md, debugging/debugging.md
│  ├─ Race conditions → debugging/flaky-tests.md, debugging/debugging.md
│  ├─ Flaky only with multiple workers → debugging/flaky-tests.md, infrastructure-ci-cd/performance.md
│  ├─ State leak / isolation → debugging/flaky-tests.md, core/fixtures-hooks.md
│  ├─ Console/JS errors → debugging/console-errors.md, debugging/debugging.md
│  └─ General debugging → debugging/debugging.md
│
├─ Testing error scenarios?
│  ├─ Network failures → debugging/error-testing.md, advanced/network-advanced.md
│  ├─ Offline (unexpected) → debugging/error-testing.md
│  ├─ Offline-first/PWA → browser-apis/service-workers.md
│  ├─ Error boundaries → debugging/error-testing.md
│  └─ Form validation → testing-patterns/forms-validation.md, debugging/error-testing.md
│
├─ Refactoring existing code?
│  ├─ Implementing POM → core/page-object-model.md
│  ├─ Improving selectors → core/locators.md
│  ├─ Extracting fixtures → core/fixtures-hooks.md
│  ├─ Creating data factories → core/test-data.md
│  └─ Configuration setup → core/configuration.md
│
├─ Setting up infrastructure?
│  ├─ CI/CD → infrastructure-ci-cd/ci-cd.md
│  ├─ GitHub Actions → infrastructure-ci-cd/github-actions.md
│  ├─ GitLab CI → infrastructure-ci-cd/gitlab.md
│  ├─ Other CI providers → infrastructure-ci-cd/other-providers.md
│  ├─ Docker/containers → infrastructure-ci-cd/docker.md
│  ├─ Sharding/parallel → infrastructure-ci-cd/parallel-sharding.md
│  ├─ Reporting/artifacts → infrastructure-ci-cd/reporting.md
│  ├─ Global setup/teardown → core/global-setup.md
│  ├─ Project dependencies → core/projects-dependencies.md
│  ├─ Test performance → infrastructure-ci-cd/performance.md
│  ├─ Test coverage → infrastructure-ci-cd/test-coverage.md
│  └─ Project config → core/configuration.md, core/projects-dependencies.md
│
├─ Organizing tests?
│  ├─ Skip/fixme/slow tests → core/annotations.md
│  ├─ Test tags (@smoke, @fast) → core/test-tags.md
│  ├─ Filtering tests (--grep) → core/test-tags.md
│  ├─ Test steps → core/annotations.md
│  └─ Conditional execution → core/annotations.md
│
└─ Running subset of tests?
   ├─ By tag (@smoke, @critical) → core/test-tags.md
   ├─ Exclude slow/flaky tests → core/test-tags.md
   ├─ PR vs nightly tests → core/test-tags.md, infrastructure-ci-cd/ci-cd.md
   └─ Project-specific filtering → core/test-tags.md, core/configuration.md

Test Validation Loop

After writing or modifying tests:

1. Run tests: npx playwright test --reporter=list
2. If tests fail:
   • Review error output and trace (npx playwright show-trace)
   • Fix locators, waits, or assertions
   • Re-run tests
3. Only proceed when all tests pass
4. Run multiple times for critical tests: npx playwright test --repeat-each=5