test-genius

test-genius is a skill for Claude Code from k1lgor/virtual-company. It costs 28 tokens per session (3,391 once invoked), scanned A, original, MIT.

A test-writing guide that requires a failing test before production code and supports test-driven development, or TDD. TDD is a method of writing a test for desired behavior before implementing that behavior.

In plain words
What is it for?
Use it to write tests, increase coverage, check edge cases, set up a test suite, or develop a feature through TDD.
Why use it?
It helps catch regressions and makes feature or bug-fix completion depend on verified behavior rather than code changes alone.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions CLAUDE.md.

Part of the virtual-company plugin — 27 skills, 1 command, 6 agents, 3 hooks shipped together

Good fit Use it to write tests, increase coverage, check edge cases, set up a test suite, or develop a feature through TDD.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/k1lgor/virtual-company/03-test-genius
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.

Any agent
npx skills add k1lgor/virtual-company --skill 03-test-genius
Clone the repo
git clone --depth 1 https://github.com/k1lgor/virtual-company

Made for: Claude Code.

Or install virtual-company, the plugin that ships this one along with the rest of its 27 skills, 1 command, 6 agents, 3 hooks.

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-genius

README.md
[![agentmods](https://agentmods.dev/badge/skills/k1lgor/virtual-company/03-test-genius/github.svg)](https://agentmods.dev/skills/k1lgor/virtual-company/03-test-genius)
Your own site
<a href="https://agentmods.dev/skills/k1lgor/virtual-company/03-test-genius"><img src="https://agentmods.dev/badge/skills/k1lgor/virtual-company/03-test-genius/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-genius

Your own site · 80×15
<a href="https://agentmods.dev/skills/k1lgor/virtual-company/03-test-genius"><img src="https://agentmods.dev/badge/skills/k1lgor/virtual-company/03-test-genius.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,391 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 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 5.1 $0.00028 $0.03391
Opus 5 $0.00014 $0.01695
Sonnet 5 $0.00006 $0.00678
Haiku 4.5 $0.00003 $0.00339

Measured 10d ago against content hash 80c72a20b88b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

test-genius 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 10d 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.

skills/03-test-genius/SKILL.md · 374 lines

How it starts

The opening of the file, as written. The whole thing — 374 lines — stays where its author put it; the contents beside it link to each section on GitHub.

🧪 Test Engineering Specialist / Test Genius

You are the Lead Quality Engineer. Code without tests is incomplete. Your mission is to ensure logical correctness and prevent regressions.

🛑 The Iron Law

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST

Write code before the test? Delete it. Start over. No exceptions — not for "simple changes," not for "just adding a field," not for "it's a config update."

🛠️ Tool Guidance

  • Reproduction: Use Read to understand the logic under test.
  • Implementation: Use Edit to create spec/test files.
  • Verification: Use Bash to analyze test runner output.

📍 When to Apply

  • "Write unit tests for this function."
  • "Increase the code coverage of this module."
  • "How do I test this edge case?"
  • "Set up a test suite for this repository."
  • "This feature needs tests before shipping."

Decision Tree: Test Writing Flow

graph TD
    A[Feature/Fix to Test] --> B{Existing test framework?}
    B -->|Yes| C[Detect framework: Jest, Pytest, Go test, etc.]
    B -->|No| D[Set up test framework first]
    D --> C
    C --> E[Write ONE failing test for next behavior]
    E --> F{Test fails for expected reason?}
    F -->|No| G[Fix test: typo, wrong assertion, wrong API]
    G --> E
    F -->|Yes| H[Write minimal implementation]
    H --> I{Test passes?}
    I -->|No| J[Fix implementation]
    J --> I
    I -->|Yes| K{Full suite green?}
    K -->|No| L[Fix regressions]
    L --> K
    K -->|Yes| M{More behaviors to test?}
    M -->|Yes| E
    M -->|No| N[Refactor if needed]
    N --> O[✅ Testing complete]

Read the full file on GitHub · 374 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. 10d ago First seen · 374 lines · 28 tokens per session scan A 80c72a20b88b

Subscribe to this mod's changes

test-genius is a skill published in the GitHub repository k1lgor/virtual-company (4 stars, last pushed 2mo ago), licensed MIT. It adds 28 tokens to every session and 3,391 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 2026-08-31.

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