anthropics/webapp-testing
skills/webapp-testing/SKILL.md
Toolkit for interacting with and testing local web applications using Playwright. Supports verifying frontend functionality, debugging UI behavior, capturing browser screenshots, and viewing browser logs.
$ install --global
skillsauthnpx skillsauth add anthropics/skills webapp-testingInstall this skill globally with one command. Works with Claude Code, Cursor, and Windsurf.
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Last scanned: Apr 21, 2026, 1:30 PM49.6s6 files scanned
SKILL.md
- name:
- webapp-testing
- description:
- Toolkit for interacting with and testing local web applications using Playwright. Supports verifying frontend functionality, debugging UI behavior, capturing browser screenshots, and viewing browser logs.
- license:
- Complete terms in LICENSE.txt
Web Application Testing
To test local web applications, write native Python Playwright scripts.
Helper Scripts Available:
scripts/with_server.py- Manages server lifecycle (supports multiple servers)
Always run scripts with --help first to see usage. DO NOT read the source until you try running the script first and find that a customized solution is abslutely necessary. These scripts can be very large and thus pollute your context window. They exist to be called directly as black-box scripts rather than ingested into your context window.
Decision Tree: Choosing Your Approach
User task → Is it static HTML?
├─ Yes → Read HTML file directly to identify selectors
│ ├─ Success → Write Playwright script using selectors
│ └─ Fails/Incomplete → Treat as dynamic (below)
│
└─ No (dynamic webapp) → Is the server already running?
├─ No → Run: python scripts/with_server.py --help
│ Then use the helper + write simplified Playwright script
│
└─ Yes → Reconnaissance-then-action:
1. Navigate and wait for networkidle
2. Take screenshot or inspect DOM
3. Identify selectors from rendered state
4. Execute actions with discovered selectors
Example: Using with_server.py
To start a server, run --help first, then use the helper:
Single server:
python scripts/with_server.py --server "npm run dev" --port 5173 -- python your_automation.py
Multiple servers (e.g., backend + frontend):
python scripts/with_server.py \
--server "cd backend && python server.py" --port 3000 \
--server "cd frontend && npm run dev" --port 5173 \
-- python your_automation.py
To create an automation script, include only Playwright logic (servers are managed automatically):
from playwright.sync_api import sync_playwright
with sync_playwright() as p:
browser = p.chromium.launch(headless=True) # Always launch chromium in headless mode
page = browser.new_page()
page.goto('http://localhost:5173') # Server already running and ready
page.wait_for_load_state('networkidle') # CRITICAL: Wait for JS to execute
# ... your automation logic
browser.close()
Reconnaissance-Then-Action Pattern
-
Inspect rendered DOM:
page.screenshot(path='/tmp/inspect.png', full_page=True) content = page.content() page.locator('button').all() -
Identify selectors from inspection results
-
Execute actions using discovered selectors
Common Pitfall
❌ Don't inspect the DOM before waiting for networkidle on dynamic apps
✅ Do wait for page.wait_for_load_state('networkidle') before inspection
Best Practices
- Use bundled scripts as black boxes - To accomplish a task, consider whether one of the scripts available in
scripts/can help. These scripts handle common, complex workflows reliably without cluttering the context window. Use--helpto see usage, then invoke directly. - Use
sync_playwright()for synchronous scripts - Always close the browser when done
- Use descriptive selectors:
text=,role=, CSS selectors, or IDs - Add appropriate waits:
page.wait_for_selector()orpage.wait_for_timeout()
Reference Files
- examples/ - Examples showing common patterns:
element_discovery.py- Discovering buttons, links, and inputs on a pagestatic_html_automation.py- Using file:// URLs for local HTMLconsole_logging.py- Capturing console logs during automation
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