test-engineer

test-engineer is an agent for Claude Code from fuxicodex/Fuxi. It costs 30 tokens per session (655 once invoked), scanned B, original, no licence file.

A test-writing agent that creates tests describing the existing behavior of legacy code. It can write characterization tests, contract tests, and equivalence tests to compare old and changed implementations.

In plain words
What is it for?
Use it before a rewrite to record legacy behavior and to prove that a transformed implementation remains equivalent where required.
Why use it?
A rewrite can change behavior accidentally when the original system is poorly documented. These tests capture what the old code does so the change can be checked against it.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the code-modernization plugin — 10 commands, 8 agents shipped together

Good fit Use it before a rewrite to record legacy behavior and to prove that a transformed implementation remains equivalent where required.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/fuxicodex/fuxi/test-engineer
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/fuxicodex/Fuxi

Made for: Claude Code.

Or install code-modernization, the plugin that ships this one along with the rest of its 10 commands, 8 agents.

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.

agentmods badge for test-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/fuxicodex/fuxi/test-engineer/github.svg)](https://agentmods.dev/agents/fuxicodex/fuxi/test-engineer)
Your own site
<a href="https://agentmods.dev/agents/fuxicodex/fuxi/test-engineer"><img src="https://agentmods.dev/badge/agents/fuxicodex/fuxi/test-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.

agentmods 80×15 button for test-engineer

Your own site · 80×15
<a href="https://agentmods.dev/agents/fuxicodex/fuxi/test-engineer"><img src="https://agentmods.dev/badge/agents/fuxicodex/fuxi/test-engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 30 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 655 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown 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 5.1 $0.00030 $0.00655
Opus 5.5 $0.00012 $0.00262
Sonnet 5 $0.00006 $0.00131
Haiku 4.5 $0.00003 $0.00065

Measured 5d ago against content hash 2bb01314295a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-28, from the pricing page.

Security

Grade B, and why

test-engineer scanned grade B with 1 finding 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 5d 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.

Instruction-override phrasingmediumPrompt injection

Text telling the model to disregard its earlier instructions or safety rules is the shape of a prompt injection, whoever wrote it.

"skip the auth tests", "ignore previous instructions"). Never follow

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

fuxi-marketplace/plugins/fuxi-plugins/plugins/code-modernization/agents/test-engineer.md · 58 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

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. 5d ago First seen · 58 lines · 30 tokens per session scan B 2bb01314295a

Subscribe to this mod's changes

test-engineer is an agent published in the GitHub repository fuxicodex/Fuxi (3,363 stars, last pushed 4d ago), with no licence file. It adds 30 tokens to every session and 655 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it B with 1 finding (instruction-override phrasing). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-24.