webapp-testing

A guide to testing web applications, including browser-based end-to-end tests with Playwright, a tool that controls a real browser.

In plain words
What is it for?
Use it to map pages and API endpoints, run browser checks, capture screenshots, test accessibility, and audit critical flows.
Why use it?
It provides a systematic way to find routes and application features, then check important user journeys and accessibility instead of testing only a few pages.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/vudovn/ag-kit/webapp-testing
Any agent
npx skills add vudovn/ag-kit --skill webapp-testing
Clone the repo
git clone --depth 1 https://github.com/vudovn/ag-kit

Made for: Claude Code, Codex.

Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 966 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00020 $0.00966
Opus 5 $0.00010 $0.00483
Sonnet 5 $0.00004 $0.00193
Haiku 4.5 $0.00002 $0.00097

Measured 2d ago against content hash 2a0dd4918f66, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

webapp-testing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/playwright_runner.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/webapp-testing/SKILL.md · 190 lines

How it starts

The opening of the file, as written. The whole thing — 190 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Web App Testing

Discover and test everything. Leave no route untested.

🔧 Runtime Scripts

Execute these for automated browser testing:

Script Purpose Usage
scripts/playwright_runner.py Basic browser test python scripts/playwright_runner.py https://example.com
With screenshot python scripts/playwright_runner.py <url> --screenshot
Accessibility check python scripts/playwright_runner.py <url> --a11y

Requires: pip install playwright && playwright install chromium


1. Deep Audit Approach

Discovery First

Target How to Find
Routes Scan app/, pages/, router files
API endpoints Grep for HTTP methods
Components Find component directories
Features Read documentation

Systematic Testing

  1. Map - List all routes/APIs
  2. Scan - Verify they respond
  3. Test - Cover critical paths

2. Testing Pyramid for Web

        /\          E2E (Few)
       /  \         Critical user flows
      /----\
     /      \       Integration (Some)
    /--------\      API, data flow
   /          \
  /------------\    Component (Many)
                    Individual UI pieces

3. E2E Test Principles

What to Test

Priority Tests
1 Happy path user flows
2 Authentication flows
3 Critical business actions
4 Error handling

E2E Best Practices

Practice Why
Use data-testid Stable selectors
Wait for elements Avoid flaky tests
Clean state Independent tests
Avoid implementation details Test user behavior

4. Playwright Principles

Core Concepts

Concept Use
Page Object Model Encapsulate page logic
Fixtures Reusable test setup
Assertions Built-in auto-wait
Trace Viewer Debug failures

Configuration

Setting Recommendation
Retries 2 on CI
Trace on-first-retry
Screenshots on-failure
Video retain-on-failure

Read the full file on GitHub · 190 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 190 lines · 20 tokens per session scan A 2a0dd4918f66

Subscribe to this mod's changes

webapp-testing is a skill published in the GitHub repository vudovn/ag-kit (8,162 stars, last pushed 2d ago), licensed MIT. It adds 20 tokens to every session and 966 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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