AGENTS.md

AI Agent Instructions for Stryker.NET

This document provides guidance for AI agents, such as GitHub Copilot, when working with the Stryker.NET repository.

Reference these instruction files when applicable:

• Always: Taming Copilot
• Always: Conventional Commit Guidelines
• Always: Security Best Practices
• Always: Self-Explanatory Code Commenting
• When writing documentation: Markdown Instructions
• When writing C#: C# Instructions
• When working with Azure Pipelines: Azure DevOps Pipelines
• When working with GitHub Actions: GitHub Actions

Reference these skill files when applicable:

• When running stryker on a project: Running Stryker
• When parsing a json stryker report: Parsing Stryker Report

Project Overview

Stryker.NET is a mutation testing framework for .NET projects. It allows you to test your tests by temporarily inserting bugs (mutations) in your source code to verify that tests catch them.

Contributing Workflow

Code Standards

• Follow the repository's .editorconfig and Microsoft C# coding guidelines
• Create or edit unit tests or integration tests for all changes
• Update documentation when adding features

Pull Request Title Convention

When creating or updating pull requests, always use Angular-style conventional commit format for PR titles:

• Format: <type>(<scope>): <subject>
• Types: feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert
• Scope: The file or group of files affected (optional but recommended)
• Subject: A short, imperative description (present tense)
• Example: feat(mutators): add string mutator support
• Example: fix(cli): resolve configuration parsing issue
• Example: docs: update contributor guidelines

Why: The project uses squash merging, so the PR title becomes the commit message in the main branch history.

Running Tests

• Unit tests: Run dotnet test in the /src directory or use your IDE's test runner
• Integration tests:
  • On Windows: Run .\integration-tests.ps1 in the root of the repo (PowerShell 7 recommended)
  • On macOS/Linux: Run pwsh ./integration-tests.ps1 in the root of the repo (requires PowerShell 7)
• Always run unit tests and integration tests after making a change to ensure nothing is broken

Testing Locally

To test Stryker.NET on a project:

1. In Stryker.CLI, open properties > Debug
2. Create a new Debug profile
3. Set Launch as Project
4. Set WorkingDirectory to a unit test project directory
5. You can use projects in .\integrationtest\TargetProjects for testing
6. Run with Stryker.CLI as the startup project

Note: Running Stryker on itself doesn't work as assemblies will be in use. To run Stryker on the stryker codebase, use the official nuget release via dotnet tool install dotnet-stryker and then dotnet stryker.

Adding a New Mutator

See the full guide in adding_a_mutator.md.