Playwright Testing

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Playwright Testing

Playwright is a modern end-to-end testing framework by Microsoft that supports Chromium, Firefox, and WebKit from a single API. It features auto-waiting on every action, built-in web-first assertions, network interception, visual regression, API testing, trace viewer, and codegen. Tests are written in TypeScript (or JavaScript) and executed with npx playwright test. The @playwright/test runner is batteries-included: parallelism, sharding, fixtures, retries, and HTML reports all come out of the box.

When to use this skill

Trigger this skill when the user:

• Writes new Playwright test files or expands an existing test suite
• Implements the Page Object Model (POM) for browser automation
• Sets up visual regression or screenshot diffing with Playwright
• Tests REST/GraphQL APIs using Playwright's request context
• Mocks or intercepts network routes during browser tests
• Debugs flaky tests or generates tests with Playwright codegen
• Configures trace viewer, test retries, or CI sharding
• Adds Playwright to a project (install, config, first test)

Do NOT trigger this skill for:

• Unit or component testing frameworks (Jest, Vitest, React Testing Library) when Playwright is not involved
• Generic browser scripting tasks unrelated to automated testing (use a browser-automation skill instead)

Key principles

1. Use auto-waiting - never add manual waits - Playwright waits automatically for elements to be actionable before every interaction. Never write page.waitForTimeout(2000) or sleep(). If a test is flaky, diagnose the root cause (network, animation, re-render) and use the correct explicit wait: page.waitForURL(), page.waitForLoadState(), or expect(locator).toBeVisible().

2. Prefer user-facing locators - Locate by role, label, placeholder, or data-testid before reaching for CSS or XPath selectors. User-facing locators are resilient to style and layout changes, and they match how assistive technology navigates the page. Priority: getByRole > getByLabel > getByPlaceholder > getByText > getByTestId > CSS/XPath.

3. Isolate tests with browser contexts - Each test should run in a fresh BrowserContext. Never share cookies, localStorage, or session state across tests. Use browser.newContext() for isolation or rely on Playwright's default per-test context. Use storageState to restore an authenticated session without repeating login flows.

4. Use web-first assertions - Always use expect(locator).toBeVisible() and similar @playwright/test assertions rather than extracting values and asserting with raw equality. Web-first assertions automatically retry until the condition passes or the timeout expires, eliminating race conditions. Never do const text = await locator.textContent(); expect(text).toBe(...) when expect(locator).toHaveText(...) exists.

5. Leverage codegen for discovery - When unsure of the best locator for an element, run npx playwright codegen <url> to record interactions and let Playwright suggest stable locators. Use the recorded output as a starting point, then refactor into page objects. Codegen also helps verify that aria roles and labels are correctly set in the application.

Core concepts

Browser / Context / Page hierarchy

Browser
  └── BrowserContext  (isolated session: cookies, localStorage, auth state)
        └── Page      (single tab / top-level frame)
              └── Frame (iframe, default is main frame)

A Browser is launched once (per worker in CI). A BrowserContext is the isolation boundary - create one per test or per authenticated user persona. A Page is a tab. Most interactions happen on Page or Frame.

Auto-waiting

Playwright performs actionability checks before every click, fill, hover, etc. An element must be:

• Attached to the DOM
• Visible (not display: none, not zero size)
• Stable (not animating)
• Enabled (not disabled)
• Receives events (not covered by another element)

If an element does not meet these conditions within the action timeout (default 30 s), the action throws with a clear timeout error.

Locator strategies

Locators are lazy references - they re-query the DOM on every use, which prevents stale element references. Compose them with .filter(), .first(), .nth(), and .locator() chaining. See references/locator-strategies.md for the full priority guide and patterns.

Fixtures

Playwright's fixture system (built into @playwright/test) enables dependency injection for pages, authenticated contexts, database state, and custom helpers. Fixtures compose via extend(). The built-in page, context, browser, browserName, request, and baseURL fixtures cover most needs; define custom fixtures for app-specific setup.

Common tasks

1. Write tests with Page Object Model

// tests/pages/LoginPage.ts
import { type Page, type Locator } from '@playwright/test'

export class LoginPage {
  private readonly emailInput: Locator
  private readonly passwordInput: Locator
  private readonly submitButton: Locator

  constructor(private readonly page: Page) {
    this.emailInput = page.getByLabel('Email')
    this.passwordInput = page.getByLabel('Password')
    this.submitButton = page.getByRole('button', { name: 'Sign in' })
  }

  async goto() {
    await this.page.goto('/login')
  }

  async login(email: string, password: string) {
    await this.emailInput.fill(email)
    await this.passwordInput.fill(password)
    await this.submitButton.click()
  }
}

// tests/auth.spec.ts
import { test, expect } from '@playwright/test'
import { LoginPage } from './pages/LoginPage'

test('user can sign in with valid credentials', async ({ page }) => {
  const loginPage = new LoginPage(page)
  await loginPage.goto()
  await loginPage.login('user@example.com', 'password123')
  await expect(page).toHaveURL('/dashboard')
  await expect(page.getByRole('heading', { name: 'Dashboard' })).toBeVisible()
})

2. Mock API routes

import { test, expect } from '@playwright/test'

test('shows error when API returns 500', async ({ page }) => {
  await page.route('**/api/users', (route) =>
    route.fulfill({
      status: 500,
      contentType: 'application/json',
      body: JSON.stringify({ error: 'Internal server error' }),
    })
  )

  await page.goto('/users')
  await expect(page.getByRole('alert')).toHaveText('Something went wrong.')
})

test('intercepts and modifies response', async ({ page }) => {
  await page.route('**/api/products', async (route) => {
    const response = await route.fetch()
    const json = await response.json()
    // Inject a test product at the top
    json.items.unshift({ id: 'test-1', name: 'Injected Product' })
    await route.fulfill({ response, json })
  })

  await page.goto('/products')
  await expect(page.getByText('Injected Product')).toBeVisible()
})

3. Visual regression with screenshots

import { test, expect } from '@playwright/test'

test('homepage matches snapshot', async ({ page }) => {
  await page.goto('/')
  // Full-page screenshot comparison
  await expect(page).toHaveScreenshot('homepage.png', {
    fullPage: true,
    threshold: 0.2, // 20% pixel diff tolerance
  })
})

test('button states match snapshots', async ({ page }) => {
  await page.goto('/design-system/buttons')
  const buttonGroup = page.getByTestId('button-group')
  await expect(buttonGroup).toHaveScreenshot('button-group.png')
})

Run npx playwright test --update-snapshots to regenerate baseline screenshots after intentional UI changes.

4. API testing with request context

import { test, expect } from '@playwright/test'

test('POST /api/users creates a user', async ({ request }) => {
  const response = await request.post('/api/users', {
    data: { name: 'Alice', email: 'alice@example.com' },
  })
  expect(response.status()).toBe(201)
  const body = await response.json()
  expect(body).toMatchObject({ name: 'Alice', email: 'alice@example.com' })
  expect(body.id).toBeDefined()
})

test('authenticated API call with shared context', async ({ playwright }) => {
  const apiContext = await playwright.request.newContext({
    baseURL: 'https://api.example.com',
    extraHTTPHeaders: { Authorization: `Bearer ${process.env.API_TOKEN}` },
  })
  const response = await apiContext.get('/me')
  expect(response.ok()).toBeTruthy()
  await apiContext.dispose()
})

5. Use fixtures for setup and teardown

// tests/fixtures.ts
import { test as base, expect } from '@playwright/test'
import { LoginPage } from './pages/LoginPage'

type AppFixtures = {
  loginPage: LoginPage
  authenticatedPage: void
}

export const test = base.extend<AppFixtures>({
  loginPage: async ({ page }, use) => {
    const loginPage = new LoginPage(page)
    await use(loginPage)
  },
  // Fixture that logs in before the test and logs out after
  authenticatedPage: async ({ page }, use) => {
    await page.goto('/login')
    await page.getByLabel('Email').fill(process.env.TEST_USER_EMAIL!)
    await page.getByLabel('Password').fill(process.env.TEST_USER_PASSWORD!)
    await page.getByRole('button', { name: 'Sign in' }).click()
    await page.waitForURL('/dashboard')

    await use()  // test runs here

    await page.goto('/logout')
  },
})

export { expect }

// tests/profile.spec.ts
import { test, expect } from './fixtures'

test('user can update profile', { authenticatedPage: undefined }, async ({ page }) => {
  await page.goto('/profile')
  await page.getByLabel('Display name').fill('Alice Updated')
  await page.getByRole('button', { name: 'Save' }).click()
  await expect(page.getByRole('status')).toHaveText('Profile saved.')
})

6. Debug with trace viewer

// playwright.config.ts
import { defineConfig } from '@playwright/test'

export default defineConfig({
  use: {
    // Collect traces on first retry of a failed test
    trace: 'on-first-retry',
    // Or always collect (useful during development):
    // trace: 'on',
  },
})

# Run tests and open trace for a failed test
npx playwright test --trace on
npx playwright show-trace test-results/path/to/trace.zip

# Open Playwright UI mode (live reloading, trace built-in)
npx playwright test --ui

The trace viewer shows a timeline of actions, network requests, console logs, screenshots, and DOM snapshots for every step - making it the fastest way to diagnose a failing test without adding console.log statements.

7. CI integration with sharding

# .github/workflows/playwright.yml
name: Playwright Tests
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        shard: [1, 2, 3, 4]  # 4 parallel shards
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm ci
      - run: npx playwright install --with-deps
      - run: npx playwright test --shard=${{ matrix.shard }}/4
      - uses: actions/upload-artifact@v4
        if: always()
        with:
          name: playwright-report-${{ matrix.shard }}
          path: playwright-report/
          retention-days: 7

// playwright.config.ts
import { defineConfig, devices } from '@playwright/test'

export default defineConfig({
  testDir: './tests',
  fullyParallel: true,
  retries: process.env.CI ? 2 : 0,
  workers: process.env.CI ? 1 : undefined,
  reporter: [['html'], ['github']],
  use: {
    baseURL: process.env.BASE_URL ?? 'http://localhost:3000',
    trace: 'on-first-retry',
  },
  projects: [
    { name: 'chromium', use: { ...devices['Desktop Chrome'] } },
    { name: 'firefox', use: { ...devices['Desktop Firefox'] } },
    { name: 'webkit', use: { ...devices['Desktop Safari'] } },
    { name: 'mobile-chrome', use: { ...devices['Pixel 5'] } },
  ],
})

Anti-patterns

Gotchas

1. storageState caches auth but does not refresh expired tokens - Saving auth state with context.storageState() and reusing it across test runs is efficient, but if the session token expires (e.g., short-lived JWTs), tests fail with mysterious 401s rather than auth errors. Add a CI step to regenerate storageState before the test run, or check token expiry in a global setup fixture.

2. page.route() intercepts only requests from that page, not from other frames - If your app loads content in iframes, API calls made from inside the iframe are not intercepted by page.route(). You must intercept at the context level using context.route() to catch all requests from any frame within that browser context.

3. toHaveScreenshot() baselines are OS and browser-engine specific - Snapshot baselines generated on macOS will not match those generated in a Linux CI environment due to font rendering and sub-pixel differences. Always generate and store baseline screenshots in the same environment where CI runs (typically Linux). Never commit macOS baselines and expect them to pass in Linux CI.

4. fullyParallel: true with shared test data causes race conditions - When tests run in parallel workers and share a database or external state (e.g., the same test user account), concurrent writes produce flaky failures that are nearly impossible to reproduce locally. Use per-test isolated data: unique email addresses generated per test run, or test fixtures that create and tear down their own data.

5. workers: 1 in CI does not prevent parallelism across shards - Setting workers: 1 in playwright.config.ts limits parallelism within a single CI job. If you're running multiple shards (--shard=1/4), each shard still runs concurrently. Tests that share global state (a single database, a shared API key) will conflict across shards even with workers: 1.

References

For detailed content on specific Playwright sub-domains, read the relevant file from the references/ folder:

• references/locator-strategies.md - Full locator priority guide, filtering, chaining, and patterns for complex DOM structures

Only load a references file if the current task requires it - they are long and will consume context.

Companion check

On first activation of this skill in a conversation: check which companion skills are installed by running ls ~/.claude/skills/ ~/.agent/skills/ ~/.agents/skills/ .claude/skills/ .agent/skills/ .agents/skills/ 2>/dev/null. Compare the results against the recommended_skills field in this file's frontmatter. For any that are missing, mention them once and offer to install:

npx skills add AbsolutelySkilled/AbsolutelySkilled --skill <name>

Skip entirely if recommended_skills is empty or all companions are already installed.