Web Application Testing

Summary

Goal: Test local web applications using native Python Playwright scripts with server lifecycle management.

Step	Action	Key Notes
1	Determine approach	Static HTML: read source for selectors; Dynamic: use server helper
2	Start server	`python scripts/with_server.py --server "cmd" --port N -- python script.py`
3	Reconnaissance	Navigate, wait for `networkidle` , screenshot/inspect DOM
4	Execute actions	Use discovered selectors with Playwright API
5	Clean up	Always close browser when done

Key Principles:

Always wait for
```
networkidle
```
before inspecting DOM on dynamic apps
Run scripts with
```
--help
```
first -- treat as black boxes, do not read source unless necessary
Use
```
sync_playwright()
```
with
```
headless=True
```
for chromium

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:

bash

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

Multiple servers (e.g., backend + frontend):

bash

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):

python

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:

python

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()

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

IMPORTANT Task Planning Notes

Always plan and break many small todo tasks
Always add a final review todo task to review the works done at the end to find any fix or enhancement needed

webapp-testing

NPX Install

SKILL.md Content