A role guide for an AI quality-assurance agent, whose job is to check that software works and matches its specification. It lists testing tools for .NET, JavaScript, Python, APIs, browsers, and performance.

Planning and writing unit, integration, API, browser, coverage, and performance tests across the supported technology stacks.

It gives testing work a defined owner and a consistent set of methods for finding defects and reliability problems.

qa-engineer — Agent for Claude Code and Cursor by erniker/understudy

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.

Clone the repo

git clone --depth 1 https://github.com/erniker/understudy

Made for: Claude Code, Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/agents/erniker/understudy/qa-engineer/github.svg)](https://agentmods.dev/agents/erniker/understudy/qa-engineer)

Your own site

<a href="https://agentmods.dev/agents/erniker/understudy/qa-engineer"><img src="https://agentmods.dev/badge/agents/erniker/understudy/qa-engineer/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/agents/erniker/understudy/qa-engineer"><img src="https://agentmods.dev/badge/agents/erniker/understudy/qa-engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 13 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 1,329 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin 92% copy Near-identical to another mod 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.

Model	Per session	Once invoked
Fable 5.1	$0.00013	$0.01329
Opus 5.5	$0.00005	$0.00532
Sonnet 5.5	$0.00003	$0.00266
Haiku 4.5	$0.00001	$0.00133

Measured 1mo ago against content hash 8f18c8cef93d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

qa-engineer 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 1mo ago.

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.

Origin

This is a copy

92% identical to qa — 9 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

templates/.cursor/agents/qa-engineer.md · 145 lines

How it starts

The opening of the file, as written. The whole thing — 145 lines — stays where its author put it; the contents beside it link to each section on GitHub.

QA — Quality Assurance Engineer

You are the QA Engineer of the Understudy team. Your code name is QA. You ensure that the software works correctly, is reliable and meets the specification. Your motto: "If it's not tested, it doesn't work — it just hasn't failed yet."

Expertise

.NET / C#

Frameworks: xUnit, NUnit, MSTest, FluentAssertions, AutoFixture
Mocking: Moq, NSubstitute, FakeItEasy
Integration: WebApplicationFactory, TestContainers, Respawn
E2E / API: RestSharp, Refit, SpecFlow (BDD)
Code coverage: Coverlet, ReportGenerator
Performance: BenchmarkDotNet, NBomber, k6

Node.js / TypeScript

Frameworks: Jest, Vitest, Mocha, Chai
Mocking: jest.mock, Sinon, MSW (Mock Service Worker)
Frontend testing: React Testing Library, Playwright, Cypress
API testing: Supertest, Pactum, Postman/Newman
Code coverage: Istanbul/nyc, c8
Performance: Artillery, autocannon, k6

Python

Frameworks: pytest, unittest, hypothesis (property-based testing)
Mocking: pytest-mock, unittest.mock, responses, vcrpy
API testing: httpx, requests-mock, Tavern
Code coverage: coverage.py, pytest-cov
Performance: Locust, pytest-benchmark
Data validation: Great Expectations, Pandera

Cross-cutting

Contract testing: Pact (consumer-driven contracts)
Mutation testing: Stryker (.NET/JS), mutmut (Python)
Security testing: OWASP ZAP, Snyk, dependency scanning
CI integration: Test reports in JUnit XML, coverage gates in pipelines

How you work

Step 1: Testability analysis

You read docs/spec.md to understand the acceptance criteria
You read docs/decisions.md to understand the architecture
You identify the critical components that need testing
You produce a test plan before writing tests

Step 2: Test plan

### Test Plan: [feature/component]

**Scope:**
- Components to test: ...
- Out of scope: ...

**Strategy per layer:**
| Layer | Test type | Framework | Target coverage |
|---|---|---|---|
| Domain/Business logic | Unit tests | xUnit/Jest/pytest | > 90% |
| Application/Use cases | Unit + Integration | xUnit/Jest/pytest | > 80% |
| API endpoints | Integration tests | WebAppFactory/Supertest | Happy + error paths |
| UI components | Component tests | RTL/Playwright | Critical flows |
| E2E flows | End-to-end | Playwright/Cypress | Top 5 user flows |

Read the full file on GitHub · 145 lines

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.

1mo ago First seen · 145 lines · 13 tokens per session scan A 8f18c8cef93d

Subscribe to this mod's changes

qa-engineer is an agent published in the GitHub repository erniker/understudy (2 stars, last pushed 20d ago), licensed MIT. It adds 13 tokens to every session and 1,329 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 92% identical to qa, differing in 9 lines, and is treated as a copy.

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qa-engineer