Playwright E2E Testing

Playwright is a strong default for modern end-to-end browser testing because it is reliable, fast enough, and built around browser automation rather than DOM mocking.

What E2E Tests Should Cover

Use E2E tests for workflows where integration between pieces matters:

• login
• checkout
• onboarding
• permissions
• critical CRUD flows

Do not use E2E for every branch of business logic. That makes suites slow and fragile.

Why Playwright

• real browser automation
• auto-waiting reduces timing flake
• network interception and tracing
• multi-browser support
• strong parallelization

Basic Example

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

test('user can sign in', async ({ page }) => {
  await page.goto('/login');
  await page.getByLabel('Email').fill('alice@example.com');
  await page.getByLabel('Password').fill('super-secret');
  await page.getByRole('button', { name: 'Sign in' }).click();

  await expect(page.getByText('Welcome back')).toBeVisible();
});

Good Practices

Use stable selectors

Prefer:

• getByRole
• getByLabel
• getByTestId

Avoid brittle CSS selectors tied to layout.

Keep setup cheap

Seed test data through APIs or fixtures instead of long UI setup when possible.

Test user outcomes

Assert things the user cares about:

• visible success state
• redirected page
• persisted record

Not internal implementation details.

Authentication Strategies

Common options:

• log in through the UI for a small number of smoke tests
• create a saved authenticated state for most tests
• mint test cookies or tokens in setup where allowed

The fastest suites usually avoid repeating the full login flow in every test.

Debugging Failures

Playwright traces are the killer feature.

Capture:

• screenshot
• video
• trace
• console logs

Then inspect the failing run instead of guessing from CI output.

Interview Answer

When would you use Playwright?

Use Playwright for critical browser workflows where real rendering, routing, auth, and network behavior need to be exercised together. Keep the suite focused on a small set of high-value journeys and rely on lower-level tests for detailed business logic.