anthropics
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.
bunx add-skill anthropics/skills -s webapp-testingLoadingβ¦
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.
User task β Is it static HTML?
ββ Yes β Read HTML file directly to identify selectors
β ββ Success β Write Playwright script using selectors
β ββ Fails/Incomplete β Treat as dynamic (below)
β
ββ No (dynamic webapp) β Is the server already running?
ββ No β Run: python scripts/with_server.py --help
β Then use the helper + write simplified Playwright script
β
ββ Yes β 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
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()
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
β Don't inspect the DOM before waiting for networkidle on dynamic apps
β
Do wait for page.wait_for_load_state('networkidle') before inspection
scripts/ can help. These scripts handle common, complex workflows reliably without cluttering the context window. Use --help to see usage, then invoke directly.sync_playwright() for synchronous scriptstext=, role=, CSS selectors, or IDspage.wait_for_selector() or page.wait_for_timeout()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 automationUse when you need to run Flow type checking, or when seeing Flow type errors in React code.
Use when you want to validate changes before committing, or when you need to check all React contribution requirements.
Use when feature flag tests fail, flags need updating, understanding @gate pragmas, debugging channel-specific test failures, or adding new flags to React.
Use when you need to check feature flag states, compare channels, or debug why a feature behaves differently across release channels.