E2e Testing

E2E Testing Expert - Playwright, Visual Regression, UI Testing

Core Expertise

• Playwright/Cypress for browser automation
• Visual regression with Percy, Chromatic, BackstopJS
• UI testing with Testing Library patterns
• Accessibility testing with axe-core
• Mobile emulation and device testing

Playwright Fundamentals

Test Structure

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

test.describe('Authentication', () => {
  test('should login successfully', async ({ page }) => {
    await page.goto('/login');
    await page.getByLabel('Email').fill('user@example.com');
    await page.getByLabel('Password').fill('password123');
    await page.getByRole('button', { name: 'Login' }).click();

    await expect(page).toHaveURL('/dashboard');
    await expect(page.getByText('Welcome')).toBeVisible();
  });
});

Page Object Model

// pages/LoginPage.ts
export class LoginPage {
  constructor(private page: Page) {}

  readonly emailInput = this.page.getByLabel('Email');
  readonly passwordInput = this.page.getByLabel('Password');
  readonly loginButton = this.page.getByRole('button', { name: 'Login' });

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

Fixtures

import { test as base } from '@playwright/test';
import { LoginPage } from './pages/LoginPage';

export const test = base.extend<{ loginPage: LoginPage }>({
  loginPage: async ({ page }, use) => {
    const loginPage = new LoginPage(page);
    await loginPage.goto();
    await use(loginPage);
  },
});

Visual Regression

Playwright Screenshots

test('homepage matches baseline', async ({ page }) => {
  await page.goto('/');
  await expect(page).toHaveScreenshot('homepage.png', {
    fullPage: true,
    animations: 'disabled',
  });
});

// Responsive screenshots
await page.setViewportSize({ width: 1920, height: 1080 });
await expect(page).toHaveScreenshot('desktop.png');

await page.setViewportSize({ width: 375, height: 667 });
await expect(page).toHaveScreenshot('mobile.png');

Percy Integration

import { percySnapshot } from '@percy/playwright';

test('visual diff with Percy', async ({ page }) => {
  await page.goto('/dashboard');
  await percySnapshot(page, 'Dashboard');
});

Chromatic (Storybook)

// package.json
{
  "scripts": {
    "chromatic": "chromatic --project-token=$CHROMATIC_PROJECT_TOKEN"
  }
}

Accessibility Testing

import AxeBuilder from '@axe-core/playwright';

test('accessibility audit', async ({ page }) => {
  await page.goto('/');

  const results = await new AxeBuilder({ page })
    .withTags(['wcag2a', 'wcag2aa'])
    .analyze();

  expect(results.violations).toEqual([]);
});

// Keyboard navigation
test('keyboard navigation', async ({ page }) => {
  await page.goto('/form');
  await page.keyboard.press('Tab');
  await expect(page.getByLabel('Email')).toBeFocused();
});

Mobile Testing

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

test.use(devices['iPhone 13 Pro']);

test('mobile navigation', async ({ page }) => {
  await page.goto('/');
  await expect(page.getByRole('button', { name: 'Menu' })).toBeVisible();
});

Network Mocking

test('mock API response', async ({ page }) => {
  await page.route('/api/users', async (route) => {
    await route.fulfill({
      status: 200,
      body: JSON.stringify([{ id: 1, name: 'John' }]),
    });
  });

  await page.goto('/users');
  await expect(page.getByText('John')).toBeVisible();
});

Debugging Flaky Tests

// Proper waiting (NOT setTimeout)
await page.waitForLoadState('networkidle');
await page.waitForSelector('.content', { state: 'visible' });

// Retry configuration
export default defineConfig({
  retries: process.env.CI ? 2 : 0,
  use: {
    trace: 'on-first-retry',
    screenshot: 'only-on-failure',
    video: 'retain-on-failure',
  },
});

CI/CD Configuration

# .github/workflows/e2e.yml
name: E2E Tests
on: [push]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - run: npx playwright install --with-deps
      - run: npm run test:e2e
      - uses: actions/upload-artifact@v3
        if: failure()
        with:
          name: playwright-report
          path: playwright-report/

Best Practices

1. Use stable locators (roles, labels, test IDs)
2. Page Object Model for maintainability
3. Wait for conditions, not timeouts
4. Isolate test data per test
5. Mock external APIs to reduce flakiness
6. Disable animations for visual tests
7. Run parallel in CI for speed
8. Save traces/screenshots on failure

Test Organization

e2e/
├── fixtures/
│   └── auth.fixture.ts
├── pages/
│   ├── LoginPage.ts
│   └── DashboardPage.ts
├── tests/
│   ├── auth.spec.ts
│   └── dashboard.spec.ts
└── playwright.config.ts

Related Skills

• qa-engineer - Overall test strategy
• unit-testing - Unit and integration tests