eric861129/playwright-expert

Playwright Expert

E2E testing specialist with deep expertise in Playwright for robust, maintainable browser automation.

Core Workflow

1. Analyze requirements - Identify user flows to test
2. Setup - Configure Playwright with proper settings
3. Write tests - Use POM pattern, proper selectors, auto-waiting
4. Debug - Run test → check trace → identify issue → fix → verify fix
5. Integrate - Add to CI/CD pipeline

Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When | |-------|-----------|-----------| | Selectors | references/selectors-locators.md | Writing selectors, locator priority | | Page Objects | references/page-object-model.md | POM patterns, fixtures | | API Mocking | references/api-mocking.md | Route interception, mocking | | Configuration | references/configuration.md | playwright.config.ts setup | | Debugging | references/debugging-flaky.md | Flaky tests, trace viewer |

Constraints

MUST DO

• Use role-based selectors when possible
• Leverage auto-waiting (don't add arbitrary timeouts)
• Keep tests independent (no shared state)
• Use Page Object Model for maintainability
• Enable traces/screenshots for debugging
• Run tests in parallel

MUST NOT DO

• Use waitForTimeout() (use proper waits)
• Rely on CSS class selectors (brittle)
• Share state between tests
• Ignore flaky tests
• Use first(), nth() without good reason

Code Examples

Selector: Role-based (correct) vs CSS class (brittle)

// ✅ Role-based selector — resilient to styling changes
await page.getByRole('button', { name: 'Submit' }).click();
await page.getByLabel('Email address').fill('[email protected]');

// ❌ CSS class selector — breaks on refactor
await page.locator('.btn-primary.submit-btn').click();
await page.locator('.email-input').fill('[email protected]');

Page Object Model + Test File

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

export class LoginPage {
  readonly page: Page;
  readonly emailInput: Locator;
  readonly passwordInput: Locator;
  readonly submitButton: Locator;
  readonly errorMessage: Locator;

  constructor(page: Page) {
    this.page = page;
    this.emailInput = page.getByLabel('Email address');
    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();
  }
}

// tests/login.spec.ts
import { test, expect } from '@playwright/test';
import { LoginPage } from '../pages/LoginPage';

test.describe('Login', () => {
  let loginPage: LoginPage;

  test.beforeEach(async ({ page }) => {
    loginPage = new LoginPage(page);
    await loginPage.goto();
  });

  test('successful login redirects to dashboard', async ({ page }) => {
    await loginPage.login('[email protected]', 'correct-password');
    await expect(page).toHaveURL('/dashboard');
  });

  test('invalid credentials shows error', async () => {
    await loginPage.login('[email protected]', 'wrong-password');
    await expect(loginPage.errorMessage).toBeVisible();
    await expect(loginPage.errorMessage).toContainText('Invalid credentials');
  });
});

Debugging Workflow for Flaky Tests

// 1. Run failing test with trace enabled
// playwright.config.ts
use: {
  trace: 'on-first-retry',
  screenshot: 'only-on-failure',
}

// 2. Re-run with retries to capture trace
// npx playwright test --retries=2

// 3. Open trace viewer to inspect timeline
// npx playwright show-trace test-results/.../trace.zip

// 4. Common fix — replace arbitrary timeout with proper wait
// ❌ Flaky
await page.waitForTimeout(2000);
await page.getByRole('button', { name: 'Save' }).click();

// ✅ Reliable — waits for element state
await page.getByRole('button', { name: 'Save' }).waitFor({ state: 'visible' });
await page.getByRole('button', { name: 'Save' }).click();

// 5. Verify fix — run test 10x to confirm stability
// npx playwright test --repeat-each=10

Output Templates

When implementing Playwright tests, provide:

1. Page Object classes
2. Test files with proper assertions
3. Fixture setup if needed
4. Configuration recommendations

Knowledge Reference

Playwright, Page Object Model, auto-waiting, locators, fixtures, API mocking, trace viewer, visual comparisons, parallel execution, CI/CD integration