# sourcefrog/cargo-mutants

:zombie: Inject bugs and see if your tests catch them!

Repository: https://github.com/sourcefrog/cargo-mutants
Canonical: https://ross.abutalabs.com/products/cargo-mutants
Homepage: https://mutants.rs/
Language: Rust
License: MIT
License Family: permissive
Topics: testing, mutation-testing, mutations, rust, rust-lang, cargo-subcommand, cargo-plugin, cargo
Last push: 2026-08-23T15:20:59+00:00

## Health v2 (maintenance only)
Score: 95/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 86, longevity 100
- inputs: {"age_days": 1820, "days_push": 10, "days_rel": 92, "gap_med": 25, "n_releases_24m": 18}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1273, forks 53 (observed 2026-08-28T04:04:12.340792+00:00)

## What it is
cargo-mutants is a mutation testing tool for Rust that automatically injects bugs (mutants) into your code and runs your test suite to see which mutants are caught. It requires no changes to your source tree and helps identify functions whose behavior is not adequately checked by tests.

## Use cases
- find gaps in my Rust test suite
- check if my tests actually verify behavior rather than just covering code
- run mutation testing on a Rust crate
- identify untested functions in a Rust project
- measure test quality beyond line coverage
- set up mutation testing in CI for pull requests

## When to choose
- you have a Rust project with reliable, non-flaky tests running under cargo test or cargo nextest
- you want to know whether tests actually check behavior, not just reach code
- you want a zero-setup mutation testing tool that works on any Rust source tree
- you want to gate pull requests on mutation testing in CI

## When to avoid
- your test suite is flaky, since results will be meaningless
- you need cross-compilation or non-Cargo build systems
- your project is not written in Rust
- your test suite is very slow, since runtime scales with mutants times test time

## Facets
- artifact type: cli-tool
- maturity: active
- function: testing, cli, developer-tools
- domain: testing, developer-tools
- platform: cli, cross-platform, windows
- tags: mutation-testing, cargo-subcommand, rust, test-quality, code-coverage-alternative, linux, macos

## Member repositories
- sourcefrog/cargo-mutants (main) score 95

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:04:12.340792+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T05:03:13.888460+00:00, confidence not recorded.
  - readme: https://github.com/sourcefrog/cargo-mutants (fetched 2026-08-28T04:04:12.340792+00:00, sha 207a08edb3d7)
  - homepage: https://mutants.rs/ (fetched 2026-08-29T12:14:30.968422+00:00, sha d860829952bd)
  - site_page: https://mutants.rs/installation.html (fetched 2026-08-29T12:14:30.972696+00:00, sha f0ee5622738d)
  - site_page: https://mutants.rs/getting-started.html (fetched 2026-08-29T12:14:30.974189+00:00, sha 9e30a0f8ea47)
  - registry_crates: https://crates.io/api/v1/crates/cargo-mutants (fetched 2026-08-29T12:14:30.975730+00:00, sha fa8b65f13113)
  - site_page: https://mutants.rs/goals.html (fetched 2026-08-29T12:14:30.970827+00:00, sha cd115c190b34)
- Data as of 2026-08-30T08:39:29.467469+00:00.