Playwright Web Testing & Automation

Comprehensive web testing skill using Playwright. Write custom JavaScript code for any testing or automation task.

Prerequisites

• Node.js: required — install from https://nodejs.org
• playwright npm package: npm install playwright (installs headless Chromium automatically)

Decision Tree: Choosing Your Approach

User task → Is server already running?
    ├─ Yes → Direct Testing
    │   ├─ Static HTML? → Navigate directly (file:// or http://)
    │   └─ Dynamic webapp? → Use Reconnaissance-Then-Action pattern
    │
    └─ No → Server Management Required
        ├─ Single server → Start server, then test
        └─ Multiple servers → Start all servers, coordinate testing

CRITICAL WORKFLOW

1. CheckTesting if server is running - Detect running dev servers OR start servers if needed
2. Write scripts to /tmp - NEVER write test files to skill directory; always use /tmp/playwright-test-*.js
3. Use visible browser by default - Always use headless: false unless user specifically requests headless mode
4. Wait for dynamic content - Use waitForLoadState('networkidle') before inspecting dynamic webapps
5. Parameterize URLs - Always make URLs configurable via constant at top of script

Reconnaissance-Then-Action Pattern

For dynamic webapps where you don't know the DOM structure upfront:

// /tmp/playwright-test-reconnaissance.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3000';

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  // STEP 1: Navigate and wait for dynamic content
  await page.goto(TARGET_URL);
  await page.waitForLoadState('networkidle'); // CRITICAL for dynamic apps

  // STEP 2: Reconnaissance - discover what's on the page
  await page.screenshot({ path: '/tmp/inspect.png', fullPage: true });
  
  const buttons = await page.locator('button').all();
  console.log(`Found ${buttons.length} buttons`);
  
  for (let i = 0; i < buttons.length; i++) {
    const text = await buttons[i].textContent();
    console.log(`  Button ${i}: "${text}"`);
  }

  // STEP 3: Action - interact with discovered elements
  const loginButton = page.locator('button:has-text("Login")');
  if (await loginButton.isVisible()) {
    await loginButton.click();
    console.log('✅ Clicked login button');
  }

  await browser.close();
})();

Server Management

Check for Running Servers

# Check if port is in use
lsof -i :3000  # Mac/Linux
netstat -ano | findstr :3000  # Windows

Start Server Before Testing

// /tmp/playwright-test-with-server.js
const { chromium } = require('playwright');
const { spawn } = require('child_process');

const TARGET_URL = 'http://localhost:3000';

(async () => {
  // Start server
  console.log('Starting server...');
  const server = spawn('npm', ['run', 'dev'], { shell: true });
  
  server.stdout.on('data', (data) => console.log(`Server: ${data}`));
  server.stderr.on('data', (data) => console.error(`Server Error: ${data}`));

  // Wait for server to be ready
  await new Promise(resolve => setTimeout(resolve, 3000));

  // Run tests
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();
  
  await page.goto(TARGET_URL);
  await page.waitForLoadState('networkidle');
  
  // Your test logic here
  console.log('Title:', await page.title());
  
  await browser.close();
  
  // Clean up server
  server.kill();
  console.log('✅ Tests complete, server stopped');
})();

Common Patterns

Test a Page (Multiple Viewports)

// /tmp/playwright-test-responsive.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false, slowMo: 100 });
  const page = await browser.newPage();

  // Desktop test
  await page.setViewportSize({ width: 1920, height: 1080 });
  await page.goto(TARGET_URL);
  console.log('Desktop - Title:', await page.title());
  await page.screenshot({ path: '/tmp/desktop.png', fullPage: true });

  // Mobile test
  await page.setViewportSize({ width: 375, height: 667 });
  await page.screenshot({ path: '/tmp/mobile.png', fullPage: true });

  await browser.close();
})();

Test Login Flow

// /tmp/playwright-test-login.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  await page.goto(`${TARGET_URL}/login`);

  await page.fill('input[name="email"]', 'test@example.com');
  await page.fill('input[name="password"]', 'password123');
  await page.click('button[type="submit"]');

  // Wait for redirect
  await page.waitForURL('**/dashboard');
  console.log('✅ Login successful, redirected to dashboard');

  await browser.close();
})();

Fill and Submit Form

// /tmp/playwright-test-form.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false, slowMo: 50 });
  const page = await browser.newPage();

  await page.goto(`${TARGET_URL}/contact`);

  await page.fill('input[name="name"]', 'John Doe');
  await page.fill('input[name="email"]', 'john@example.com');
  await page.fill('textarea[name="message"]', 'Test message');
  await page.click('button[type="submit"]');

  // Verify submission
  await page.waitForSelector('.success-message');
  console.log('✅ Form submitted successfully');

  await browser.close();
})();

Check for Broken Links

const { chromium } = require('playwright');

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  await page.goto('http://localhost:3000');

  const links = await page.locator('a[href^="http"]').all();
  const results = { working: 0, broken: [] };

  for (const link of links) {
    const href = await link.getAttribute('href');
    try {
      const response = await page.request.head(href);
      if (response.ok()) {
        results.working++;
      } else {
        results.broken.push({ url: href, status: response.status() });
      }
    } catch (e) {
      results.broken.push({ url: href, error: e.message });
    }
  }

  console.log(`✅ Working links: ${results.working}`);
  console.log(`❌ Broken links:`, results.broken);

  await browser.close();
})();

Take Screenshot with Error Handling

const { chromium } = require('playwright');

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  try {
    await page.goto('http://localhost:3000', {
      waitUntil: 'networkidle',
      timeout: 10000,
    });

    await page.screenshot({
      path: '/tmp/screenshot.png',
      fullPage: true,
    });

    console.log('📸 Screenshot saved to /tmp/screenshot.png');
  } catch (error) {
    console.error('❌ Error:', error.message);
  } finally {
    await browser.close();
  }
})();

Test Responsive Design

// /tmp/playwright-test-responsive-full.js
const { chromium } = require('playwright');

const TARGET_URL = 'http://localhost:3001'; // Auto-detected

(async () => {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();

  const viewports = [
    { name: 'Desktop', width: 1920, height: 1080 },
    { name: 'Tablet', width: 768, height: 1024 },
    { name: 'Mobile', width: 375, height: 667 },
  ];

  for (const viewport of viewports) {
    console.log(
      `Testing ${viewport.name} (${viewport.width}x${viewport.height})`,
    );
 & Discovery

```javascript
// Check visibility
const isVisible = await page.locator('button').isVisible();

// Get text
const text = await page.locator('h1').textContent();

// Get attribute
const href = await page.locator('a').getAttribute('href');

// Find all elements
const allButtons = await page.locator('button').all();
const allLinks = await page.locator('a').all();

// Check if element exists
const count = await page.locator('.modal').count();
console.log(`Found ${count} modals`);

Network & Console

// Intercept requests
await page.route('**/api/**', route => {
  route.fulfill({
    status: 200,
    body: JSON.stringify({ mocked: true })
  });
});

// Wait for response
const response = await page.waitForResponse('**/api/data');
console.log(await response.json());

// Capture console logs
page.on('console', msg => {
  console.log(`Browser console [${msg.type()}]:`, msg.text());
});

Best Practices

✅ DO

• Wait for networkidle on dynamic apps - Always use page.waitForLoadState('networkidle') before inspecting DOM on SPAs/React/Vue apps
• Use reconnaissance pattern - Take screenshot, inspect DOM, then act based on what you find
• Visible browser by default - Use headless: false for easier debugging
• Descriptive selectors - Use text=, role=, or data attributes over brittle CSS selectors
• Error handling - Wrap automation in try-catch blocks
• Clean up resources - Always close browser and kill servers

❌ DON'T

• Don't inspect before networkidle - On dynamic webapps, DOM may not be ready yet
• Don't use fixed timeouts - Use waitForSelector() or waitForLoadState() instead of arbitrary waits
• Don't write to skill directory - Always use /tmp for test scripts
• Don't hardcode URLs - Use constants at top of script for easy modificationeadless: false, // Visible browser slowMo: 50 // Slow down by 50ms });

const page = await browser.newPage();

// Navigate await page.goto('https://example.com', { waitUntil: 'networkidle' // Wait for network to be idle });

// Close await browser.close();

### Selectors & Interactions

```javascript
// Click
await page.click('button.submit');
await page.dblclick('.item');

// Fill input
await page.fill('input[name="email"]', 'test@example.com');
await page.getByLabel('Email').fill('user@example.com');

// Checkbox
await page.check('input[type="checkbox"]');
await page.uncheck('input[type="checkbox"]');

// Select dropdown
await page.selectOption('select#country', 'usa');

// Type with delay
await page.type('#username', 'testuser', { delay: 100 });

Waiting Strategies

// Wait for navigation
await page.waitForURL('**/dashboard');
await page.waitForLoadState('networkidle');

// Wait for element
await page.waitForSelector('.success-message');
await page.waitForSelector('.spinner', { state: 'hidden' });

// Wait for timeout (use sparingly)
await page.waitForTimeout(1000);

Screenshots

// Full page screenshot
await page.screenshot({
  path: '/tmp/screenshot.png',
  fullPage: true
});

// Element screenshot
await page.locator('.chart').screenshot({
  path: '/tmp/chart.png'
});
```Quick Tips

- **Visible browser** - Always `headless: false` unless explicitly requested
- **Write to /tmp** - Scripts go to `/tmp/playwright-test-*.js`, never to project directories
- **Parameterize URLs** - Use `TARGET_URL` constant at top of script
- **Slow down** - Use `slowMo: 100` to see actions in real-time
- **Wait smart** - Use `waitForLoadState('networkidle')` for dynamic apps before inspecting
- **Error handling** - Wrap in try-catch with proper cleanup in finally block
- **Progress feedback** - Use `console.log()` to
const text = await page.locator('h1').textContent();

// Get attribute
const href = await page.locator('a').getAttribute('href');

Network

// Intercept requests
await page.route('**/api/**', route => {
  route.fulfill({
    status: 200,
    body: JSON.stringify({ mocked: true })
  });
});

// Wait for response
const response = await page.waitForResponse('**/api/data');
console.log(await response.json());

Tips

• DEFAULT: Visible browser - Always use headless: false unless user explicitly asks for headless mode
• Use /tmp for test files - Write to /tmp/playwright-test-*.js, never to skill directory or user's project
• Parameterize URLs - Put detected/provided URL in a TARGET_URL constant at the top of every script
• Slow down: Use slowMo: 100 to make actions visible and easier to follow
• Wait strategies: Use waitForURL, waitForSelector, waitForLoadState instead of fixed timeouts
• Error handling: Always use try-catch for robust automation
• Console output: Use console.log() to track progress and show what's happening

Common Use Cases

Visual Testing:

• Take screenshots at different viewports
• Compare visual changes
• Test responsive design

Functional Testing:

• Test login flows
• Form validation
• Navigation flows
• Error handling

Validation:

• Check for broken links
• Verify images load
• Test page load times
• Check accessibility

Automation:

• Fill forms automatically
• Click through user flows
• Extract data from pages
• Generate reports

Notes

• Each automation is custom-written for your specific request
• Not limited to pre-built scripts - any browser task possible
• Auto-detects running dev servers to eliminate hardcoded URLs
• Test scripts written to /tmp for automatic cleanup (no clutter)
• Progressive disclosure - load advanced documentation only when needed

References

• Playwright Documentation
• Playwright API Reference
• Best Practices