webapp-testing skill | PlugMCP

webapp-testing

by anthropics182k

Toolkit for interacting with and testing local web applications using Playwright. Supports verifying frontend functionality, debugging UI behavior, capturing browser screenshots, and viewing browser l

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Use withClaudeCursorCodex

The file stays in the publisher's repository. PlugMCP does not host or rewrite it.

Download skill skills/webapp-testing/SKILL.md on GitHub

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name: webapp-testing description: 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. license: Complete terms in LICENSE.txt

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

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

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

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

webapp-testing

Install

Related skills

name: webapp-testing description: 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. license: Complete terms in LICENSE.txt

Web Application Testing

Decision Tree: Choosing Your Approach

Example: Using with_server.py

Reconnaissance-Then-Action Pattern

Common Pitfall

Best Practices

Reference Files