Playwright
Overview
Playwright is a browser automation framework for Node.js and Python supporting Chromium, Firefox, and WebKit with a single API. It provides auto-waiting, web-first assertions, and full test isolation for reliable end-to-end testing.
When to use: Browser automation, web scraping, screenshot/PDF generation, API testing, configuring Playwright Test, troubleshooting Playwright errors, stealth mode and anti-bot bypass.
When NOT to use: Simple HTTP requests (use fetch), unit testing (use Vitest/Jest), serverless scraping at scale (consider Cloudflare Browser Rendering). For E2E test architecture (Page Object Models, CI sharding, test organization, authentication patterns), use the e2e-testing skill.
Quick Reference
| Pattern | API / Config | Key Points |
|---|---|---|
| Basic test | test('name', async ({page}) => {}) | Auto-wait, web-first assertions, test isolation |
| Locator | page.getByRole() / page.locator() | Prefer role/label/text selectors over CSS |
| Assertion | expect(locator).toBeVisible() | Auto-retrying, configurable timeout |
| API testing | request fixture / apiRequestContext | Send HTTP requests, validate responses |
| Aria snapshot | expect(locator).toMatchAriaSnapshot() | Validate accessibility tree structure via YAML |
| Class assertion | expect(locator).toContainClass('active') | Match individual CSS class names (v1.52+) |
| Visible filter | locator.filter({visible: true}) | Match only visible elements (v1.51+) |
| Test step | test.step('name', async (step) => {}) | Timeout, skip, and attachments (v1.50+) |
| Stealth mode | playwright-extra + stealth plugin | Patches 20+ detection vectors |
| Authenticated session | context.cookies() + addCookies() | Save/restore cookies and IndexedDB for persistence |
| Screenshot | page.screenshot({fullPage: true}) | Wait for key elements to load first |
| PDF generation | page.pdf({format: 'A4'}) | Chromium only, set printBackground: true |
| Clock API | page.clock | Freeze, fast-forward, or simulate time in tests |
| A11y assertions | toHaveAccessibleName, toHaveRole | Native assertions without axe-core dependency |
| Viewport assertion | expect(locator).toBeInViewport() | Assert element is within the visible viewport |
| Changed tests only | --only-changed=$GITHUB_BASE_REF | Run only test files changed since base branch |
| Docker | mcr.microsoft.com/playwright:v1.58.2-noble | Use --init --ipc=host flags |
| Debug methods | page.consoleMessages() / page.requests() (v1.56+) | No event listeners needed |
| Speedboard | HTML reporter (v1.57+) | Identifies slow tests and bottlenecks |
| Playwright Agents | npx playwright init-agents | Planner, generator, healer for LLM-driven testing |
| Flaky test detection | --fail-on-flaky-tests (v1.50+) | Exit code 1 on flaky tests in CI |
| Modify live responses | route.fetch() + route.fulfill() | Intercept real response, tweak JSON, return it |
| Soft assertions | expect.soft(locator) | Don't stop test on failure, report all at end |
| Retry block | expect(async () => {}).toPass() | Default timeout is 0 (forever) — always set one |
| Custom matchers | expect.extend() / mergeExpects() | Define or combine custom assertion methods |
| Actionability matrix | Per-action auto-wait checks | click: all 5 checks, fill: 3, focus/blur: none |
| Test modifiers | test.fixme() / test.fail() / test.slow() | fixme=skip+track, fail=assert failure, slow=3x |
| Parallel modes | test.describe.configure({mode: 'serial'}) | serial, parallel, or default per-describe block |
| Teardown projects | teardown option on setup projects | Auto-cleanup after all dependents finish |
Common Mistakes
| Mistake | Correct Pattern |
|---|---|
| Using CSS selectors over role selectors | Prefer getByRole, getByLabel, getByText for resilience |
| Not closing browser | Always await browser.close() in finally block |
Using setTimeout for waits | Use locator auto-wait or waitForLoadState |
page.pause() left in CI code | Guard with if (!process.env.CI) — hangs CI indefinitely |
| Clicking without waiting | Use locator().click() with built-in auto-wait |
| Shared state between tests | Each test gets fresh context via fixtures |
| Testing implementation details | Assert user-visible behavior, not DOM structure |
| Hardcoded waits for dynamic content | Wait for selector appearance or content stabilization |
Missing await on assertions | All expect() assertions return promises — must be awaited |
| Same user agent for all scraping | Rotate user agents for high-volume scraping |
Using setTimeout for time-dependent tests | Use page.clock API to freeze/fast-forward time |
| Installing axe-core for simple a11y checks | Use native toHaveAccessibleName/toHaveRole assertions |
Using toPass() without explicit timeout | Always pass {timeout: 10_000} — default is 0 (forever) |
Service worker silently blocking page.route() | Set serviceWorkers: 'block' in context config when using MSW |
Using fill() for autocomplete/debounce inputs | Use pressSequentially() with optional delay for per-keystroke handling |
storageState losing sessionStorage | storageState only saves cookies + localStorage — inject sessionStorage via addInitScript() |
Delegation
- Selector troubleshooting: Use
Exploreagent - Test pattern review: Use
Taskagent - Code review: Delegate to
code-revieweragent
For E2E test architecture, Page Object Model patterns, CI sharding strategies, authentication flows, visual regression workflows, or test organization, use the e2e-testing skill.References
- Quick start and installation
- E2E testing patterns and assertions
- Selector strategies and best practices
- Configuration and Docker deployment
- Docker and CI
- Debug methods and performance analysis
- Common automation patterns
- Stealth mode and anti-bot bypass
- Known issues and solutions
- Site-specific blocking and bypasses
- Troubleshooting common problems
- Network testing, mocking, and API patterns
- Input patterns, actionability, and test modifiers
- Advanced assertions, polling, custom matchers, and annotations
- Advanced topics: MCP, AI agents, parallel contexts