Web Application Testing

Toolkit for interacting with and testing local web applications using Playwright. Verify frontend functionality, debug UI behavior, capture screenshots, and view browser logs.

Prerequisites

• •Python with Playwright installed
• •Local web application to test
• •Understanding of web selectors

Instructions

Decision Tree

Is it static HTML?
├─ Yes → Read HTML file directly for selectors
│        → Write Playwright script
└─ No (dynamic webapp)
   ├─ Server not running → Use with_server.py helper
   └─ Server running → Reconnaissance-then-action pattern

Using with_server.py

Single server:

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

Playwright Script Template

from playwright.sync_api import sync_playwright

with sync_playwright() as p:
    browser = p.chromium.launch(headless=True)
    page = browser.new_page()
    page.goto('http://localhost:5173')
    page.wait_for_load_state('networkidle')  # CRITICAL for dynamic apps
    # ... automation logic
    browser.close()

Reconnaissance-Then-Action

1. •

   Inspect rendered DOM:

   python

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

2. •

   Identify selectors from inspection

3. •

   Execute actions using discovered selectors

Best Practices

• •Always wait for networkidle before DOM inspection
• •Use sync_playwright() for synchronous scripts
• •Always close browser when done
• •Use descriptive selectors: text=, role=, CSS, IDs

Error Handling

• •Don't inspect DOM before waiting for networkidle
• •Add waits: page.wait_for_selector() or page.wait_for_timeout()
• •Use bundled scripts as black boxes - run --help first

Notes

• •Helper scripts handle common workflows reliably
• •Examples: element_discovery.py, static_html_automation.py
• •Capture console logs with console_logging.py

Source: anthropics/skills