MCPGateway: Skill for Codex

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

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