What is mcaf-dotnet-stryker?

A guide for using Stryker.NET, a free .NET mutation-testing tool. Mutation testing makes small changes to code and checks whether the tests detect them.

Measuring test strength in critical .NET projects, especially high-risk code, while controlling the runtime cost of mutation-testing runs.

Normal test coverage shows which code runs, but not whether tests catch faults. Stryker.NET helps reveal important code paths whose tests may be too weak.

mcaf-dotnet-stryker — Skill by managedcode

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 skills/managedcode/mcpgateway/mcaf-dotnet-stryker

Any agent

npx skills add managedcode/MCPGateway --skill mcaf-dotnet-stryker

Clone the repo

git clone --depth 1 https://github.com/managedcode/MCPGateway

Made for: Claude Code, Codex.

Per session 46 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 869 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin 100% 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.

Model	Per session	Once invoked
Fable 5	$0.00046	$0.00869
Opus 5	$0.00023	$0.00434
Sonnet 5	$0.00009	$0.00174
Haiku 4.5	$0.00005	$0.00087

Measured 2d ago against content hash 0d451bdf4913, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mcaf-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 2d 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

100% identical to mcaf-dotnet-stryker — 0 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.

.codex/skills/mcaf-dotnet-stryker/SKILL.md · 105 lines

How it starts

The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCAF: .NET 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

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

Workflow

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

Bootstrap When Missing

If Stryker.NET is not configured yet:

Detect current state:
- rg --files -g '.config/dotnet-tools.json'
- dotnet tool list --local
- dotnet tool list --global
Prefer local tool installation for reproducible CI:
- dotnet new tool-manifest (if missing)
- dotnet tool install dotnet-stryker
Choose a focused target scope and mutation budget before enabling CI.
Add a dedicated mutation command in AGENTS.md and CI (not in the fastest PR path by default).
Run dotnet stryker on the target project and return status: configured or status: improved.
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 · 105 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.

references/stryker.md 880 B

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.

2d ago First seen · 105 lines · 46 tokens per session scan A 0d451bdf4913

Subscribe to this mod's changes

mcaf-dotnet-stryker is a skill published in the GitHub repository managedcode/MCPGateway (5 stars, last pushed 2d ago), licensed MIT. It adds 46 tokens to every session and 869 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to mcaf-dotnet-stryker, differing in 0 lines, and is treated as a copy.

Research Testing ai-extensions csharp dotnet embeddings mcp mcp-gateway

mcaf-dotnet-stryker