webapp-testing

Web Application Testing

To test local web applications, write native Python Playwright scripts.

Use this skill when the task needs local server lifecycle management, custom Python assertions, or a repeatable test script. For ad-hoc browser navigation and interaction that does not need custom Python, use $playwright-cli.

Helper Scripts Available:

• scripts/with_server.py - Manages server lifecycle (supports multiple servers)

Always run helper scripts with --help first to see usage. DO NOT read the source until you try running the helper and find that a customized solution is absolutely 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.

Dependency Preflight

Before writing a native Playwright script, verify the selected project environment:

uv run python -c "from importlib.metadata import version; print(version('playwright'))"

If the import fails:

1. For a one-off page inspection without custom assertions, use the declared $playwright-cli fallback.

2. For repeatable assertions or managed server testing, ask before installing dependencies. After approval, install into the project's development environment rather than adding a browser runtime to production dependencies:

   uv pip install --python <project>/.venv/bin/python playwright
   uv run python -m playwright install chromium
   

3. Re-run the import preflight, then continue with native Python Playwright.

If the project already declares a Playwright dev extra, prefer syncing that extra over an ad-hoc environment install. Never use bare pip or a machine-global Python environment.

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: uv 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