playwright-expert

SKILL.md

Playwright Expert

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

Core Workflow

Analyze requirements - Identify user flows to test

Setup - Configure Playwright with proper settings

Write tests - Use POM pattern, proper selectors, auto-waiting

Debug - Run test → check trace → identify issue → fix → verify fix

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('user@example.com');

// ❌ CSS class selector — breaks on refactor
await page.locator('.btn-primary.submit-btn').click();
await page.locator('.email-input').fill('user@example.com');

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('user@example.com', 'correct-password');
    await expect(page).toHaveURL('/dashboard');
  });

  test('invalid credentials shows error', async () => {
    await loginPage.login('user@example.com', '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:

Page Object classes

Test files with proper assertions

Fixture setup if needed

Configuration recommendations

Knowledge Reference

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

Documentation