Playwright Test Automation

Step 1 — Determine Execution Target

Decide BEFORE writing any code:

Step 2 — Detect Language

Step 3 — Determine Scope

Core Patterns — TypeScript (Default)

Selector Priority

Use in this order — stop at the first that works:

1. getByRole('button', { name: 'Submit' }) — accessible, resilient
2. getByLabel('Email') — form fields
3. getByPlaceholder('Enter email') — when label missing
4. getByText('Welcome') — visible text
5. getByTestId('submit-btn') — last resort, needs data-testid

Never use raw CSS/XPath unless matching a third-party widget with no other option.

Assertions — Always Web-First

// ✅ Auto-retries until timeout
await expect(page.getByRole('heading')).toBeVisible();
await expect(page.getByRole('alert')).toHaveText('Saved');
await expect(page).toHaveURL('/dashboard');

// ❌ No auto-retry — races with DOM
const text = await page.textContent('.msg');
expect(text).toBe('Saved');

Anti-Patterns

Page Object Model

Use POM for any project with more than 3 tests. Full patterns with base page, fixtures, and examples in reference/page-object-model.md.

Quick example:

// pages/login.page.ts
import { Page, Locator } from '@playwright/test';

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

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

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

Configuration — Local

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

export default defineConfig({
  testDir: './tests',
  timeout: 30_000,
  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-chrome', use: { ...devices['Pixel 5'] } },
    { name: 'mobile-safari', use: { ...devices['iPhone 13'] } },
  ],
  webServer: {
    command: 'npm run dev',
    port: 3000,
    reuseExistingServer: !process.env.CI,
  },
});

Cloud Execution on TestMu AI

Set environment variables: LT_USERNAME, LT_ACCESS_KEY

Direct CDP connection (standard approach):

// lambdatest-setup.ts
import { chromium } from 'playwright';

const capabilities = {
  browserName: 'Chrome',
  browserVersion: 'latest',
  'LT:Options': {
    platform: 'Windows 11',
    build: 'Playwright Build',
    name: 'Playwright Test',
    user: process.env.LT_USERNAME,
    accessKey: process.env.LT_ACCESS_KEY,
    network: true,
    video: true,
    console: true,
  },
};

const browser = await chromium.connect({
  wsEndpoint: `wss://cdp.lambdatest.com/playwright?capabilities=${encodeURIComponent(JSON.stringify(capabilities))}`,
});
const context = await browser.newContext();
const page = await context.newPage();

HyperExecute project approach (for parallel cloud runs):

// Add to projects array in playwright.config.ts:
{
  name: 'chrome:latest:Windows 11@lambdatest',
  use: { viewport: { width: 1920, height: 1080 } },
},
{
  name: 'MicrosoftEdge:latest:macOS Sonoma@lambdatest',
  use: { viewport: { width: 1920, height: 1080 } },
},

Run: npx playwright test --project="chrome:latest:Windows 11@lambdatest"

Test Status Reporting (Cloud)

Tests on TestMu AI show "Completed" by default. You MUST report pass/fail:

// In afterEach or test teardown:
await page.evaluate((_) => {},
  `lambdatest_action: ${JSON.stringify({
    action: 'setTestStatus',
    arguments: { status: testInfo.status, remark: testInfo.error?.message || 'OK' },
  })}`
);

This is handled automatically when using the fixture from reference/cloud-integration.md.

Validation Workflow

After generating any test:

1. Validate config:  python scripts/validate-config.py playwright.config.ts
2. If errors → fix → re-validate
3. Run locally:      npx playwright test --project=chromium
4. If cloud:         npx playwright test --project="chrome:latest:Windows 11@lambdatest"
5. If failures → check reference/debugging-flaky.md

Quick Reference

Common Commands

npx playwright test                          # Run all tests
npx playwright test --ui                     # Interactive UI mode
npx playwright test --debug                  # Step-through debugger
npx playwright test --project=chromium       # Single browser
npx playwright test tests/login.spec.ts      # Single file
npx playwright show-report                   # Open HTML report
npx playwright codegen https://example.com   # Record test
npx playwright test --update-snapshots       # Update visual baselines

Auth State Reuse

// Save auth state once in global setup
await page.context().storageState({ path: 'auth.json' });

// Reuse in config
use: { storageState: 'auth.json' }

Visual Regression (Built-in)

await expect(page).toHaveScreenshot('homepage.png', {
  maxDiffPixelRatio: 0.01,
  animations: 'disabled',
  mask: [page.locator('.dynamic-date')],
});

Network Mocking

await page.route('**/api/users', (route) =>
  route.fulfill({ json: [{ id: 1, name: 'Mock User' }] })
);

Full mocking patterns in reference/api-mocking-visual.md.

Test Steps for Readability

test('checkout flow', async ({ page }) => {
  await test.step('Add item to cart', async () => {
    await page.goto('/products');
    await page.getByRole('button', { name: 'Add to cart' }).click();
  });

  await test.step('Complete checkout', async () => {
    await page.getByRole('link', { name: 'Cart' }).click();
    await page.getByRole('button', { name: 'Checkout' }).click();
  });
});

Reference Files

Advanced Playbook

For production-grade patterns, see reference/playbook.md: