Claude Code Plugins

Open-source plugins for Claude Code — AI-powered developer tools that extend Claude's capabilities with specialized workflows.

Prerequisites

• Claude Code CLI installed and authenticated
• For mutation-guard: Go 1.21+ (other languages coming soon)

Plugins

Plugin	What It Does	Languages	Status
mutation-guard	Test quality analysis via mutation testing — detects false confidence where high coverage hides weak assertions	Go (PHP, Node.js, Java, Rust planned)	✅ Active

Quick Start

1. Install the plugin

claude plugins add github:rezafarzaneh7/claude-code-plugins/plugins/mutation-guard

2. Open Claude Code in your project

cd ~/projects/my-go-service
claude

3. Analyze and fix

# See where your tests have gaps
/mutation-guard ./services

# Auto-write tests that close those gaps
/mutation-guard-fix ./services

Full Example

# Install the plugin (one-time)
$ claude plugins add github:rezafarzaneh7/claude-code-plugins/plugins/mutation-guard

# Navigate to your Go project
$ cd ~/projects/my-api

# Start Claude Code
$ claude

# Inside Claude Code — analyze your handlers package
> /mutation-guard ./internal/handlers

# Claude will:
#   1. Detect Go from go.mod
#   2. Install go-mutesting if missing
#   3. Run coverage analysis
#   4. Run mutation testing
#   5. Produce a quality report with impact analysis

# Now fix the gaps it found
> /mutation-guard-fix ./internal/handlers

# Claude will:
#   1. Read your existing test patterns
#   2. Write tests that kill survived mutants
#   3. Verify all new tests pass
#   4. Show a before/after comparison

Example Output

Quality Report

## Mutation Guard — Quality Report

**Project**: my-service  |  **Language**: Go  |  **Scope**: ./services

### TL;DR

| Metric          | Score  | Trend |
|-----------------|--------|-------|
| Coverage        | 72.4%  | 🆕    |
| Mutation Score  | 58.3%  | 🆕    |
| Quality Verdict | ⚠️ False Confidence | ⚠️ |

High coverage masks weak assertions — 5 critical gaps found.

### Quality Matrix

| # | File            | Coverage | Mutation | Verdict             |
|---|-----------------|----------|----------|---------------------|
| 1 | handler.go      | 89.2%    | 42.1%    | ⚠️ False Confidence  |
| 2 | service.go      | 76.5%    | 71.4%    | 🟡 Partial           |
| 3 | repository.go   | 45.0%    | 33.3%    | 🔴 Critical           |

Fix Report

### TL;DR

> 7 tests written | 5 mutants killed
> Coverage: 72.4% → 84.1% (↑ +11.7%)
> Mutation Score: 58.3% → 78.9% (↑ +20.6%)

How It Works

1. Detect — auto-identifies project language from build files (go.mod, package.json, etc.)
2. Coverage — runs language-native coverage tools to measure what code tests execute
3. Mutate — injects small bugs (mutants) and checks if tests catch them
4. Impact — classifies survived mutants by production risk (Critical → High → Medium)
5. Fix — writes missing tests that kill survived mutants, matching your existing test patterns

The key insight: coverage measures what tests touch, mutation score measures what tests catch. A file with 90% coverage and 40% mutation score has tests that run the code without actually verifying behavior.

Supported Languages

Language	Coverage Tool	Mutation Tool	Status
Go	go test -cover	go-mutesting	✅ Active
PHP	phpunit --coverage	Infection	🔜 Planned
Node.js	jest --coverage / nyc	Stryker	🔜 Planned
Java	jacoco	PIT	🔜 Planned
Rust	cargo tarpaulin	cargo-mutants	🔜 Planned

Contributing

See CONTRIBUTING.md for how to add a new plugin or improve an existing one.

License

MIT