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