Webapp Testing

This is a toolkit for interacting with and testing local web applications using Playwright. It supports verifying frontend functionality, debugging UI behavior, capturing browser screenshots, and viewing browser logs.

Key Helper Scripts

• 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 absolutely necessary.

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

Single Server

python scripts/with_server.py --server "npm run dev" --port 5173 -- python your_automation.py

Multiple Servers

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

Automation Script Template

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

1. Inspect rendered DOM:

   page.screenshot(path='/tmp/inspect.png', full_page=True)
   content = page.content()
   page.locator('button').all()
   

2. Identify selectors from inspection results

3. 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 - Use --help to see usage, then invoke directly without reading source
• 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/ - 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