dotnet-stryker

dotnet-stryker is a skill for Claude Code, Codex from Postpartum-genushyacinthus29/dotnet-skills. It costs 44 tokens per session (888 once invoked), scanned A, a copy of stryker, MIT.

A .NET mutation-testing tool that changes code in small ways to test whether the test suite detects the faults.

In plain words
What is it for?
Use it to assess tests for critical .NET projects and libraries, usually outside the fastest pull-request checks.
Why use it?
Code coverage shows which lines run, but not whether tests would catch broken behavior. Mutation testing exposes weak tests in important code.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions AGENTS.md.

Good fit Use it to assess tests for critical .NET projects and libraries, usually outside the fastest pull-request checks.

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Install with agentmods
npx agentmods add skills/postpartum-genushyacinthus29/dotnet-skills/dotnet-stryker
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 Postpartum-genushyacinthus29/dotnet-skills --skill dotnet-stryker
Clone the repo
git clone --depth 1 https://github.com/Postpartum-genushyacinthus29/dotnet-skills

Made for: Claude Code, Codex.

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 dotnet-stryker

README.md
[![agentmods](https://agentmods.dev/badge/skills/postpartum-genushyacinthus29/dotnet-skills/dotnet-stryker/github.svg)](https://agentmods.dev/skills/postpartum-genushyacinthus29/dotnet-skills/dotnet-stryker)
Your own site
<a href="https://agentmods.dev/skills/postpartum-genushyacinthus29/dotnet-skills/dotnet-stryker"><img src="https://agentmods.dev/badge/skills/postpartum-genushyacinthus29/dotnet-skills/dotnet-stryker/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 dotnet-stryker

Your own site · 80×15
<a href="https://agentmods.dev/skills/postpartum-genushyacinthus29/dotnet-skills/dotnet-stryker"><img src="https://agentmods.dev/badge/skills/postpartum-genushyacinthus29/dotnet-skills/dotnet-stryker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 888 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 91% copy Near-identical to another mod 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 $0.00044 $0.00888
Opus 5 $0.00022 $0.00444
Sonnet 5 $0.00009 $0.00178
Haiku 4.5 $0.00004 $0.00089

Measured 9d ago against content hash 5d758afb6284, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

dotnet-stryker 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 9d 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.

Origin

This is a copy

91% identical to stryker — 14 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/dotnet-stryker/SKILL.md · 109 lines

How it starts

The opening of the file, as written. The whole thing — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Stryker.NET

Trigger On

  • the repo uses or wants Stryker.NET
  • mutation testing is needed for high-risk code

Value

  • produce a concrete project delta: code, docs, config, tests, CI, or review artifact
  • reduce ambiguity through explicit planning, verification, and final validation skills
  • leave reusable project context so future tasks are faster and safer

Do Not Use For

  • every PR path by default in a large repo
  • simple coverage collection

Inputs

  • the nearest AGENTS.md
  • target projects and critical paths
  • time budget for mutation runs

Quick Start

  1. Read the nearest AGENTS.md and confirm scope and constraints.
  2. Run this skill's Workflow through the Ralph Loop until outcomes are acceptable.
  3. Return the Required Result Format with concrete artifacts and verification evidence.

Workflow

  1. Run mutation testing on critical projects, not blindly on the whole mono-repo.
  2. Keep it out of the fastest PR path unless the repo explicitly accepts the runtime cost.
  3. Stabilize tests first; mutation testing amplifies flaky or slow suites.

Bootstrap When Missing

If Stryker.NET is not configured yet:

  1. Detect current state:
    • rg --files -g '.config/dotnet-tools.json'
    • dotnet tool list --local
    • dotnet tool list --global
  2. Prefer local tool installation for reproducible CI:
    • dotnet new tool-manifest (if missing)
    • dotnet tool install dotnet-stryker
  3. Choose a focused target scope and mutation budget before enabling CI.
  4. Add a dedicated mutation command in AGENTS.md and CI (not in the fastest PR path by default).
  5. Run dotnet stryker on the target project and return status: configured or status: improved.
  6. If mutation testing is explicitly out of scope, return status: not_applicable.

Deliver

  • explicit mutation-test scope
  • reproducible Stryker commands

Validate

  • the selected scope is affordable in CI
  • mutation score is interpreted with test quality, not as a vanity number

Read the full file on GitHub · 109 lines

Files

What ships with it

3 files 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. 9d ago First seen · 109 lines · 44 tokens per session scan A 5d758afb6284

Subscribe to this mod's changes

dotnet-stryker is a skill published in the GitHub repository Postpartum-genushyacinthus29/dotnet-skills (10 stars, last pushed 2d ago), licensed MIT. It adds 44 tokens to every session and 888 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 91% identical to stryker, differing in 14 lines, and is treated as a copy.