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 --help to 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() or page.wait_for_timeout() Reference Files examples/ - Examples showing common patterns: element_discovery.py - Discovering buttons, links, and inputs on a page static_html_automation.py - Using file:// URLs for local HTML console_logging.py - Capturing console logs during automation