Mutagoph

Mutagoph (pronounced mew-ta-goph) - mutate + gopher

A mutation testing framework for Go, designed for large monorepos with a focus on speed and quality.

Features

• 23 Mutation Operators - Arithmetic, comparison, logical, assignment, and control flow
• 4 Mutation Sets - lite, standard, thorough, mutilated
• Adaptive Parallelism - Dynamic worker spawning for long-running mutations
• Git Integration - Diff-based incremental testing
• Multiple Outputs - Terminal, JSON, HTML reports
• Caching - Skip unchanged mutations
• Quality Gates - CI threshold enforcement
• Coverage Filter - Skip uncovered code (marked as Naked)
• Watch Mode - Continuous testing during development

Installation

# Using Go
go install github.com/its-donkey/mutagoph/cmd/mutagoph@latest

# Using Homebrew (macOS/Linux)
brew install its-donkey/tap/mutagoph

Or download a pre-built binary from Releases.

Quick Start

# Run mutation testing
mutagoph run

# Run with specific mutation set
mutagoph run --mutations standard

# Generate HTML report
mutagoph run --output html --output-file report.html

# Skip testing uncovered code (faster)
mutagoph run --coverage-filter

# Watch mode
mutagoph watch

Documentation

Full documentation available at its-donkey.github.io/mutagoph

• Quick Start - Get up and running
• Configuration - YAML config and environment variables
• Mutation Operators - All 23 operators explained
• CLI Reference - Complete flag documentation

Basic Example

// Your code
func Add(a, b int) int {
    return a + b
}

// Mutagoph generates mutations like:
// return a - b  (arithmetic_replace)
// return a      (arithmetic_delete)
// return 0      (return_replace)

If your tests catch these mutations, they're "killed". If tests still pass, they "survive" - indicating gaps in test coverage.

Requirements

• Go 1.23+

License

Mutagoph is dual-licensed:

• AGPL-3.0 - Free for open source projects. If you modify Mutagoph or use it in a network service, you must release your source code under AGPL-3.0.
• Commercial License - For proprietary use without AGPL obligations. Contact Jeff Shapiro for licensing inquiries.

See LICENSE for the full AGPL-3.0 text.