1---
2name: webapp-testing
3description: 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.
4license: Complete terms in LICENSE.txt
5---
6 
7# Web Application Testing
8 
9To test local web applications, write native Python Playwright scripts.
10 
11**Helper Scripts Available**:
12- `scripts/with_server.py` - Manages server lifecycle (supports multiple servers)
13 
14**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.
15 
16## Decision Tree: Choosing Your Approach
17 
18```
19User task → Is it static HTML?
20    ├─ Yes → Read HTML file directly to identify selectors
21    │         ├─ Success → Write Playwright script using selectors
22    │         └─ Fails/Incomplete → Treat as dynamic (below)
23    │
24    └─ No (dynamic webapp) → Is the server already running?
25        ├─ No → Run: python scripts/with_server.py --help
26        │        Then use the helper + write simplified Playwright script
27        │
28        └─ Yes → Reconnaissance-then-action:
29            1. Navigate and wait for networkidle
30            2. Take screenshot or inspect DOM
31            3. Identify selectors from rendered state
32            4. Execute actions with discovered selectors
33```
34 
35## Example: Using with_server.py
36 
37To start a server, run `--help` first, then use the helper:
38 
39**Single server:**
40```bash
41python scripts/with_server.py --server "npm run dev" --port 5173 -- python your_automation.py
42```
43 
44**Multiple servers (e.g., backend + frontend):**
45```bash
46python scripts/with_server.py \
47  --server "cd backend && python server.py" --port 3000 \
48  --server "cd frontend && npm run dev" --port 5173 \
49  -- python your_automation.py
50```
51 
52To create an automation script, include only Playwright logic (servers are managed automatically):
53```python
54from playwright.sync_api import sync_playwright
55 
56with sync_playwright() as p:
57    browser = p.chromium.launch(headless=True) # Always launch chromium in headless mode
58    page = browser.new_page()
59    page.goto('http://localhost:5173') # Server already running and ready
60    page.wait_for_load_state('networkidle') # CRITICAL: Wait for JS to execute
61    # ... your automation logic
62    browser.close()
63```
64 
65## Reconnaissance-Then-Action Pattern
66 
671. **Inspect rendered DOM**:
68   ```python
69   page.screenshot(path='/tmp/inspect.png', full_page=True)
70   content = page.content()
71   page.locator('button').all()
72   ```
73 
742. **Identify selectors** from inspection results
75 
763. **Execute actions** using discovered selectors
77 
78## Common Pitfall
79 
80❌ **Don't** inspect the DOM before waiting for `networkidle` on dynamic apps
81✅ **Do** wait for `page.wait_for_load_state('networkidle')` before inspection
82 
83## Best Practices
84 
85- **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. 
86- Use `sync_playwright()` for synchronous scripts
87- Always close the browser when done
88- Use descriptive selectors: `text=`, `role=`, CSS selectors, or IDs
89- Add appropriate waits: `page.wait_for_selector()` or `page.wait_for_timeout()`
90 
91## Reference Files
92 
93- **examples/** - Examples showing common patterns:
94  - `element_discovery.py` - Discovering buttons, links, and inputs on a page
95  - `static_html_automation.py` - Using file:// URLs for local HTML
96  - `console_logging.py` - Capturing console logs during automation