etylsarin/playwright-testing

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Playwright Testing

For project-specific test configuration and breakpoints, see testing-config.md.

Commands

npx playwright test                       # Run all tests
npx playwright test --ui                  # Open interactive UI mode
npx playwright test --headed              # Run with visible browsers
npx playwright test auth.spec.ts          # Run specific spec
npx playwright test --project=chromium    # Run in specific browser
npx playwright test --grep "login"        # Filter by test name
npx playwright test --debug               # Step-through debugging
npx playwright codegen http://localhost:3000  # Generate tests from actions
npx playwright show-report                # View HTML test report
npx playwright install                    # Install browsers

File Conventions

Tests: tests/e2e/{feature}/, page objects: tests/pages/, fixtures: tests/fixtures/.

Writing Tests

Basic Test Pattern

import { test, expect } from '@playwright/test';
import { LoginPage } from '../pages/login-page';

test.describe('Login', () => {
  test('submits valid credentials', async ({ page }) => {
    const login = new LoginPage(page);
    await login.goto();
    await login.fill('[email protected]', 'password123');
    await page.getByRole('button', { name: 'Sign in' }).click();
    await expect(page.getByTestId('dashboard')).toBeVisible();
  });
});

API Mocking

// Mock API responses for deterministic tests
await page.route('/api/login', (route) => {
  route.fulfill({ status: 200, body: JSON.stringify({ token: 'test' }) });
});

Locator Strategy

Prefer semantic locators; avoid brittle CSS selectors:

page.getByRole('button', { name: 'Sign in' })   // preferred: ARIA role + accessible name
page.getByLabel('Email address')                  // form inputs by label
page.getByTestId('login-form')                    // test-id for complex containers
page.getByText('Welcome back')                    // visible text
page.locator('[data-state="open"]')               // CSS only when no semantic alternative

Quick Workflow: Write → Run → Debug → Verify

1. Write a focused spec using page objects and test.describe.
2. Run locally with npx playwright test --ui to iterate interactively.
3. On failure: collect a trace (trace: 'on-first-retry'), save an HTML report, and inspect via npx playwright show-report.
4. Validation checkpoint: confirm npx playwright show-report shows 0 failures and that saved traces contain the failing trace id.
5. Fix the test or app; re-run the spec and verify the HTML report is green.

Configuration (playwright.config.ts)

import { defineConfig, devices } from '@playwright/test';

export default defineConfig({
  testDir: './tests',
  fullyParallel: true,
  forbidOnly: !!process.env.CI,
  retries: process.env.CI ? 2 : 0,
  workers: process.env.CI ? 1 : undefined,
  reporter: [['html'], ['list']],
  use: {
    baseURL: 'http://localhost:3000',
    trace: 'on-first-retry',
    screenshot: 'only-on-failure',
  },
  projects: [
    { name: 'chromium', use: { ...devices['Desktop Chrome'] } },
    { name: 'firefox', use: { ...devices['Desktop Firefox'] } },
    { name: 'webkit', use: { ...devices['Desktop Safari'] } },
    { name: 'mobile', use: { ...devices['iPhone 14'] } },
  ],
  webServer: {
    command: 'npm run dev',
    url: 'http://localhost:3000',
    reuseExistingServer: !process.env.CI,
  },
});

See REFERENCE.md for MCP tools and advanced config (moved to a referenced file).

Best Practices (non-obvious)

• Use trace: 'on-first-retry' selectively for flaky suites; attach trace IDs to failure tickets
• Favor page-object reuse across specs but avoid global singletons that leak state between parallel workers
• For CI visual diffs, snapshot only stable regions and mask dynamic content before comparison