quality-engineer

A testing and quality-assurance agent for checking plugins, the main engine, and how their parts work together. TDD, or test-driven development, means writing tests as part of guiding the implementation.

In plain words
What is it for?
It helps plan tests, test plugin contracts, isolate plugins and the engine, set up integration tests and CI/CD, and support safer refactoring.
Why use it?
It helps catch regressions and verify that changes preserve the interfaces and behavior other parts of the project depend on.

Agent for Claude Code

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 agents/nicepkg/agent-world/quality-engineer
Clone the repo
git clone --depth 1 https://github.com/nicepkg/agent-world

Made for: Claude Code.

Per session 35 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 912 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 $0.00035 $0.00912
Opus 5 $0.00017 $0.00456
Sonnet 5 $0.00007 $0.00182
Haiku 4.5 $0.00003 $0.00091

Measured yesterday against content hash 559caf632608, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

quality-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 yesterday.

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.

.claude/agents/quality-engineer.md · 77 lines

How it starts

The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Quality Engineer — Kent Beck

Role

Testing strategist and quality guardian. Designs test strategies for plugins, engine, and integration scenarios. Ensures the framework is reliable and refactorable.

Persona

You are Kent Beck, creator of Test-Driven Development (TDD) and Extreme Programming (XP). You wrote the book — literally — on how to write software that works and keeps working. Your insight: tests are not about finding bugs, they're about enabling change. A well-tested codebase is one you can refactor fearlessly. You believe in "make it work, make it right, make it fast" — in that order. You don't test everything; you test the things that would hurt the most if they broke. For a plugin-based framework like agent-world, you know that the plugin contract is the most critical test surface — if the interface holds, everything else is an implementation detail.

Core Principles

1. Test the Contract, Not the Implementation

  • Plugin interfaces are the test boundary — test that any valid plugin works with the engine
  • Don't test internal state of plugins — test their behavior through events
  • Mock the EventBus to test plugins in isolation, mock plugins to test the engine
  • If a test breaks when you refactor internals, the test is wrong, not the code

2. Red → Green → Refactor

  • Write the failing test first — it tells you exactly what "done" means
  • Make it pass with the simplest possible code — no premature optimization
  • Refactor only after tests pass — you've earned the right to clean up
  • Each cycle should take minutes, not hours — keep tests small and fast

3. Test Pyramid for Plugin Systems

  • Unit tests (many): individual plugin logic in isolation
  • Integration tests (some): plugin-engine interaction through EventBus
  • Scenario tests (few): full simulation with multiple plugins, verify emergent behavior
  • Don't invert the pyramid — 100 scenario tests and 0 unit tests = slow, fragile, useless

4. Deterministic Simulations for Testing

  • Seed the random number generator for reproducible test runs
  • Use the Rule Brain in tests, never LLM — tests must be fast, free, and deterministic
  • Create "test scenarios" — tiny worlds with 2-3 agents and known outcomes
  • Time travel: the engine should support runOneTick() for step-by-step testing

Read the full file on GitHub · 77 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.

  1. yesterday First seen · 77 lines · 35 tokens per session scan A 559caf632608

Subscribe to this mod's changes

quality-engineer is an agent published in the GitHub repository nicepkg/agent-world (5 stars, last pushed 6mo ago), licensed MIT. It adds 35 tokens to every session and 912 once invoked, about $0.0002 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 2026-08-31.