Web Application Testing with Playwright

Overview

Playwright is a powerful framework for web testing and automation that supports all modern browsers (Chromium, Firefox, WebKit). It provides reliable, fast, and capable automation with auto-waiting, network control, and comprehensive testing capabilities.

Use this skill when you need to:

• Create end-to-end tests for web applications
• Automate browser interactions and workflows
• Test across multiple browsers and devices
• Verify UI/UX functionality and accessibility
• Mock APIs and intercept network requests
• Capture screenshots and videos for debugging

Core Capabilities

Multi-Browser Testing

• Chromium (Chrome, Edge, Brave)
• Firefox (Mozilla Firefox)
• WebKit (Safari engine)
• Cross-browser compatibility testing
• Parallel execution across browsers

Element Interaction

• Click, double-click, right-click
• Type text with realistic keyboard simulation
• Select dropdowns and checkboxes
• Hover and focus interactions
• Drag and drop operations
• File uploads and downloads

Assertions & Verification

• Element visibility and state checks
• Text content verification
• Attribute validation
• URL and navigation assertions
• Custom expect matchers
• Soft assertions for multiple checks

Screenshot & Video Capture

• Full page screenshots
• Element-specific captures
• Video recording of test sessions
• Visual comparison testing
• Trace files for debugging

Network Interception

• Mock API responses
• Intercept and modify requests
• Monitor network traffic
• Test offline scenarios
• Performance monitoring

Mobile Device Emulation

• 100+ device presets (iPhone, Pixel, iPad, etc.)
• Custom viewport configurations
• Touch event simulation
• Geolocation testing
• Orientation changes

Core Testing Workflow

1. Basic Test Setup

Create a simple test with Playwright's auto-waiting:

import pytest
from playwright.sync_api import Page, expect

def test_homepage_loads(page: Page):
    """Test that homepage loads successfully."""
    page.goto("https://example.com")
    expect(page).to_have_title("Example Domain")
    expect(page.locator("h1")).to_contain_text("Example Domain")

def test_navigation(page: Page):
    """Test navigation between pages."""
    page.goto("https://example.com")
    page.click("text=More information")
    expect(page).to_have_url("https://www.iana.org/domains/reserved")

2. Form Interactions

Test form filling, validation, and submission:

def test_login_form(page: Page):
    """Test login form submission."""
    page.goto("https://example.com/login")

    # Fill form fields
    page.fill("#username", "testuser@example.com")
    page.fill("#password", "SecurePassword123")
    page.check("#remember-me")

    # Submit and verify
    page.click("button[type='submit']")
    expect(page).to_have_url("https://example.com/dashboard")
    expect(page.locator(".welcome-message")).to_be_visible()

3. API Mocking

Mock API responses for controlled testing:

def test_with_mocked_api(page: Page):
    """Test with mocked API response."""
    # Mock API response
    page.route("**/api/user", lambda route: route.fulfill(
        status=200,
        content_type="application/json",
        body='{"name": "Test User", "premium": true}'
    ))

    page.goto("https://example.com/profile")
    expect(page.locator(".user-name")).to_contain_text("Test User")

4. Mobile Emulation

Test responsive designs on mobile devices:

@pytest.fixture
def mobile_page(playwright):
    """Create mobile browser context."""
    iphone = playwright.devices['iPhone 12']
    browser = playwright.chromium.launch()
    context = browser.new_context(**iphone)
    page = context.new_page()
    yield page
    context.close()
    browser.close()

def test_mobile_menu(mobile_page: Page):
    """Test mobile navigation."""
    mobile_page.goto("https://example.com")
    expect(mobile_page.locator(".hamburger-menu")).to_be_visible()
    mobile_page.click(".hamburger-menu")
    expect(mobile_page.locator(".mobile-menu")).to_be_visible()

5. Visual Regression

Capture screenshots for visual comparison:

def test_homepage_screenshot(page: Page):
    """Capture homepage screenshot."""
    page.goto("https://example.com")

    # Full page screenshot
    page.screenshot(path="screenshots/homepage.png", full_page=True)

    # Element screenshot
    page.locator("header").screenshot(path="screenshots/header.png")

    # Screenshot with masks for dynamic content
    page.screenshot(
        path="screenshots/dashboard.png",
        mask=[page.locator(".timestamp"), page.locator(".session-id")]
    )

Key Testing Principles

Use Reliable Selectors

# ✅ GOOD: Test IDs and semantic selectors
page.click("[data-testid='submit-button']")
page.click("button:text('Submit')")
page.click("role=button[name='Submit']")

# ❌ BAD: Fragile structural selectors
page.click("div > div > button:nth-child(3)")

Leverage Auto-Waiting

# ✅ GOOD: Playwright auto-waits
page.click("button")
expect(page.locator(".result")).to_be_visible()

# ⚠️ Avoid: Manual waits
time.sleep(2)  # Only when absolutely necessary

Ensure Test Isolation

# ✅ GOOD: Clean state between tests
@pytest.fixture(autouse=True)
def clear_state(page: Page):
    yield
    page.context.clear_cookies()
    page.evaluate("localStorage.clear()")

Handle Flaky Tests

# ✅ GOOD: Wait for specific conditions
page.click("button")
page.wait_for_selector(".result")
result = page.locator(".result").text_content()

# ✅ GOOD: Use soft assertions
expect.soft(page.locator(".title")).to_be_visible()
expect.soft(page.locator(".price")).to_contain_text("$")

Page Object Model

Organize tests using the Page Object pattern for maintainability:

class LoginPage:
    """Login page object."""

    def __init__(self, page: Page):
        self.page = page
        self.username_input = page.locator("#username")
        self.password_input = page.locator("#password")
        self.submit_button = page.locator("button[type='submit']")

    def login(self, username: str, password: str):
        """Perform login."""
        self.username_input.fill(username)
        self.password_input.fill(password)
        self.submit_button.click()

# Use in tests
def test_login(page: Page):
    login_page = LoginPage(page)
    login_page.login("test@example.com", "password123")
    expect(page).to_have_url("/dashboard")

Common Test Patterns

Authentication

@pytest.fixture
def authenticated_page(page: Page):
    """Provide authenticated session."""
    page.goto("https://example.com/login")
    page.fill("#username", "test@example.com")
    page.fill("#password", "password")
    page.click("button[type='submit']")
    page.wait_for_url("**/dashboard")
    yield page

File Operations

# Upload
page.set_input_files("#file-input", "path/to/file.pdf")

# Download
with page.expect_download() as download_info:
    page.click("a:text('Download')")
download = download_info.value
download.save_as("downloads/file.pdf")

Network Monitoring

requests = []
page.on("request", lambda req: requests.append(req))
page.goto("https://example.com")

# Verify API calls were made
api_requests = [r for r in requests if "/api/" in r.url]
assert len(api_requests) > 0

Running Tests

Basic Commands

# Install Playwright
pip install playwright pytest-playwright
playwright install

# Run all tests
pytest tests/

# Run specific browser
pytest --browser chromium --browser firefox

# Run in headed mode (see browser)
pytest --headed

# Debug mode
PWDEBUG=1 pytest tests/test_login.py

# Parallel execution
pytest -n auto

# Generate test code
playwright codegen https://example.com

Configuration

See references/setup-configuration.md for:

• Complete installation instructions
• Project structure setup
• pytest.ini configuration
• playwright.config.ts for TypeScript
• CI/CD integration examples

Quality Standards

Ensure tests meet these criteria:

• Tests are independent and can run in any order
• Selectors are reliable (test IDs, semantic selectors)
• Proper error handling and assertions
• Screenshots/videos captured on failure
• No hardcoded waits (use auto-waiting)
• Clean state management between tests

Additional Resources

Detailed Documentation

• Setup & Configuration - Installation, project structure, and configuration
• Best Practices - Selector strategies, wait patterns, flaky test prevention
• Common Pitfalls - Race conditions, selector brittleness, cleanup issues
• CI/CD Integration - GitHub Actions, Docker, deployment pipelines

Code Examples

• Login Testing - Authentication flows and session management
• Form Testing - Form validation, file uploads, dropdowns
• E-commerce Testing - Shopping cart, checkout flows, coupons
• API Mocking - Network interception, mocking, monitoring
• Mobile Testing - Device emulation, touch events, responsive design
• Page Object Model - POM pattern implementation

Helper Scripts

• Playwright Helper - Utility functions for common Playwright operations
• Test Examples - Complete test suite examples

External Resources

• Official Documentation: https://playwright.dev
• Python API: https://playwright.dev/python/docs/intro
• TypeScript API: https://playwright.dev/docs/intro
• Best Practices: https://playwright.dev/docs/best-practices
• Community Discord: https://aka.ms/playwright/discord

Troubleshooting

Tests are flaky:

• Use Playwright's auto-waiting instead of manual sleeps
• Ensure proper wait conditions (wait_for_selector, wait_for_url)
• Use expect() assertions which auto-retry

Selectors not finding elements:

• Verify element exists with browser DevTools
• Use Playwright Inspector: PWDEBUG=1 pytest test.py
• Try multiple selector strategies (text, role, test-id)

Tests slow in CI:

• Enable parallel execution: pytest -n auto
• Use headed mode only for debugging
• Consider browser context reuse for related tests

For more troubleshooting tips, see Common Pitfalls.