e2e-testing

End-to-End Testing Patterns (Playwright)

Setup

npm init playwright@latest
npx playwright install  # Install browsers

// playwright.config.ts
import { defineConfig, devices } from '@playwright/test'
export default defineConfig({
  testDir: './tests/e2e',
  fullyParallel: true,
  retries: process.env.CI ? 2 : 0,
  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: 'Mobile Safari', use: { ...devices['iPhone 13'] } },
  ],
  webServer: {
    command: 'npm run dev',
    url: 'http://localhost:3000',
    reuseExistingServer: !process.env.CI,
  },
})

Page Object Model

// tests/e2e/pages/LoginPage.ts
import { Page, Locator } from '@playwright/test'
export class LoginPage {
  readonly emailInput: Locator
  readonly passwordInput: Locator
  readonly submitButton: Locator
  readonly errorMessage: Locator

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

  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()
  }
}

Writing Tests

import { test, expect } from '@playwright/test'
import { LoginPage } from './pages/LoginPage'

test.describe('Authentication', () => {
  test('login with valid credentials', async ({ page }) => {
    const loginPage = new LoginPage(page)
    await loginPage.goto()
    await loginPage.login('[email protected]', 'password123')
    await expect(page).toHaveURL('/dashboard')
  })

  test('show error for invalid credentials', async ({ page }) => {
    const loginPage = new LoginPage(page)
    await loginPage.goto()
    await loginPage.login('[email protected]', 'wrong')
    await expect(loginPage.errorMessage).toContainText('Invalid credentials')
  })
})