mutation-strategies

mutation-strategies is a skill for Claude Code from willmarple/harness-visualizer. It costs 51 tokens per session (3,078 once invoked), scanned A, original, no licence file.

A guide to mutation testing with Stryker and Vitest. Mutation testing changes code in small ways to check whether the test suite detects those changes.

In plain words
What is it for?
Use it to interpret mutation reports and improve TypeScript tests so they detect more defects.
Why use it?
It helps reveal tests that pass but fail to catch realistic code mistakes.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Part of the qa plugin — 5 skills, 5 commands, 5 agents shipped together

Good fit Use it to interpret mutation reports and improve TypeScript tests so they detect more defects.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/willmarple/harness-visualizer/mutation-strategies
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 willmarple/harness-visualizer --skill mutation-strategies
Clone the repo
git clone --depth 1 https://github.com/willmarple/harness-visualizer

Made for: Claude Code.

Or install qa, the plugin that ships this one along with the rest of its 5 skills, 5 commands, 5 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 mutation-strategies

README.md
[![agentmods](https://agentmods.dev/badge/skills/willmarple/harness-visualizer/mutation-strategies.svg)](https://agentmods.dev/skills/willmarple/harness-visualizer/mutation-strategies)
Your own site
<a href="https://agentmods.dev/skills/willmarple/harness-visualizer/mutation-strategies"><img src="https://agentmods.dev/badge/skills/willmarple/harness-visualizer/mutation-strategies.svg" alt="Measured on agentmods" height="20"></a>
Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,078 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 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 $0.00051 $0.03078
Opus 5 $0.00026 $0.01539
Sonnet 5 $0.00010 $0.00616
Haiku 4.5 $0.00005 $0.00308

Measured 8d ago against content hash f95bf7f22f46, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

mutation-strategies 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 8d 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.

.claude/plugins/claude-qa/skills/mutation-strategies/SKILL.md · 429 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

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. 8d ago First seen · 429 lines · 51 tokens per session scan A f95bf7f22f46

Subscribe to this mod's changes

mutation-strategies is a skill published in the GitHub repository willmarple/harness-visualizer (17 stars, last pushed 3mo ago), with no licence file. It adds 51 tokens to every session and 3,078 once invoked, about $0.0003 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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