cargo-mutants iconcargo-mutants

oss Free Star0k

Mutation testing for Rust: inject bugs and see if your tests catch them. Fast, parallel execution finds gaps in test coverage.

—
650 GitHub Stars
Rust Language
2022 Released

Overview

cargo-mutants is a mutation testing tool for Rust that helps find gaps in test coverage by deliberately injecting bugs into your code. It systematically creates variants (mutants) of your codebase and runs your test suite against each one. If a mutant survives (tests still pass despite the bug), it indicates a gap in testing. The tool features parallel execution, smart filtering to avoid trivial mutations, and integration with Cargo's build system for seamless workflow integration.

The Verdict

Who Should Use cargo-mutants?

Best For

  • Rust projects wanting to improve test quality beyond coverage metrics
  • Teams seeking to identify gaps in edge case testing
  • Critical codebases requiring high test confidence

Not Ideal For

  • Projects with very slow test suites (mutation testing is time-intensive)
  • Early-stage prototypes where test investment is low

What's Great

  • Finds real test coverage gaps that line coverage misses
  • Parallel execution speeds up mutation testing
  • Smart filtering avoids trivial or equivalent mutants
  • Integrates seamlessly with Cargo workflow
  • Detailed reports show which mutants survived
GitHub Repository

Watch Out For

  • Can be time-consuming even with parallelization
  • Requires well-structured test suite for meaningful results
  • May generate false positives for equivalent mutants
  • Resource-intensive for large codebases
Community Feedback

Pricing

Open Source
$0
Free and open source under MIT license. Available via cargo install.
View all features & details

Key Features

  • Automatic mutation generation from Rust source
  • Parallel test execution across mutants
  • Smart filtering of trivial mutations
  • JSON and text output formats
  • Integration with CI/CD pipelines
  • Incremental testing support

Platforms

  • Linux (x86_64, aarch64)
  • macOS (Intel, Apple Silicon)
  • Windows (x86_64)
  • Requires Rust toolchain

How It Compares

Feature cargo-mutants PITest (Java) Stryker (JS/TS)
Language Rust Java JavaScript/TypeScript
Speed Fast (parallel) Fast Moderate
Mutation Types Rust-specific Comprehensive Comprehensive
CI Integration Yes Yes Yes
Pricing Free/OSS Free/OSS Free/OSS
Best For Rust projects Java projects JS/TS projects

User Reviews

Loading reviews...