add-mutation-testing

add-mutation-testing is a command for coding agents from davepoon/buildwithclaude. It costs 6 tokens per session (714 once invoked), scanned A, original, MIT.

A command for setting up mutation testing, a method that changes code in small ways to check whether the test suite notices. It covers choosing a framework, configuring changes and file scope, and connecting the checks to continuous integration.

In plain words
What is it for?
Use it to assess test quality and configure mutation testing for JavaScript, TypeScript, Java, C#, Python, Go, Rust, or PHP projects.
Why use it?
A high test count does not prove that tests catch real bugs. Mutation testing exposes weak tests by showing which deliberate code changes pass unnoticed.

Command

Part of the all-commands plugin — 23 commands shipped together

About the project

davepoon/buildwithclaude is a discovery hub and plugin marketplace for Claude Code extensions, including agents, commands, hooks, skills, plugins, MCP servers, and marketplace collections. Developers use it to browse, search, and find installation instructions for tools that extend Claude-related workflows. Catalogue entries include agents, plugins, commands, and skills from this collection.

davepoon/buildwithclaude · 3,415 stars · on GitHub · buildwithclaude.com

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 commands/davepoon/buildwithclaude/add-mutation-testing
Clone the repo
git clone --depth 1 https://github.com/davepoon/buildwithclaude

Or install all-commands, the plugin that ships this one along with the rest of its 23 commands.

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 add-mutation-testing

README.md
[![agentmods](https://agentmods.dev/badge/commands/davepoon/buildwithclaude/add-mutation-testing.svg)](https://agentmods.dev/commands/davepoon/buildwithclaude/add-mutation-testing)
Your own site
<a href="https://agentmods.dev/commands/davepoon/buildwithclaude/add-mutation-testing"><img src="https://agentmods.dev/badge/commands/davepoon/buildwithclaude/add-mutation-testing.svg" alt="Measured on agentmods" height="20"></a>
Per session 6 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 714 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 5.1 $0.00006 $0.00714
Opus 5 $0.00003 $0.00357
Sonnet 5 $0.00001 $0.00143
Haiku 4.5 $0.00001 $0.00071

Measured today against content hash 2041eabfe391, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

add-mutation-testing 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 today.

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.

plugins/all-commands/commands/add-mutation-testing.md · 85 lines

How it starts

The opening of the file, as written. The whole thing — 85 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Add Mutation Testing

Setup mutation testing for code quality

Instructions

  1. Mutation Testing Strategy Analysis

    • Analyze current test suite coverage and quality
    • Identify critical code paths and business logic for mutation testing
    • Assess existing testing infrastructure and CI/CD integration points
    • Determine mutation testing scope and performance requirements
    • Plan mutation testing integration with existing quality gates
  2. Mutation Testing Tool Selection

    • Choose appropriate mutation testing framework:
      • JavaScript/TypeScript: Stryker, Mutode
      • Java: PIT (Pitest), Major
      • C#: Stryker.NET, VisualMutator
      • Python: mutmut, Cosmic Ray, MutPy
      • Go: go-mutesting, mut
      • Rust: mutagen, cargo-mutants
      • PHP: Infection
    • Consider factors: language support, performance, CI integration, reporting
  3. Mutation Testing Configuration

    • Install and configure mutation testing framework
    • Set up mutation testing configuration files and settings
    • Configure mutation operators and strategies
    • Set up file and directory inclusion/exclusion rules
    • Configure performance and timeout settings
  4. Mutation Operator Configuration

    • Configure arithmetic operator mutations (+, -, *, /, %)
    • Set up relational operator mutations (<, >, <=, >=, ==, !=)
    • Configure logical operator mutations (&&, ||, !)
    • Set up conditional boundary mutations (< to <=, > to >=)
    • Configure statement deletion and insertion mutations
  5. Test Execution and Performance

    • Configure mutation test execution strategy and parallelization
    • Set up incremental mutation testing for large codebases
    • Configure mutation testing timeouts and resource limits
    • Set up mutation test caching and optimization
    • Configure selective mutation testing for changed code
  6. Quality Metrics and Thresholds

    • Set up mutation score calculation and reporting
    • Configure mutation testing thresholds and quality gates
    • Set up mutation survival analysis and reporting
    • Configure test effectiveness metrics and tracking
    • Set up mutation testing trend analysis

Read the full file on GitHub · 85 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. today First seen · 85 lines · 6 tokens per session scan A 2041eabfe391

Subscribe to this mod's changes

add-mutation-testing is a command published in the GitHub repository davepoon/buildwithclaude (3,415 stars, last pushed yesterday), licensed MIT. It adds 6 tokens to every session and 714 once invoked, about $0.0000 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 2026-09-05.