cargo-mutants

Spec sheet

Purpose

cargo-mutants is a mutation testing tool for Rust that finds places where bugs could be inserted without causing tests to fail.Read 5 Oct 2026 · mutants.rs

Support

The project README invites users to share experience reports in GitHub Discussions and sponsor development.Read 5 Oct 2026 · github.com

Build system limit

Build tools other than Cargo are not currently supported.Read 5 Oct 2026 · mutants.rs

CI

The manual includes instructions and examples for testing mutants in CI, including incremental pull request testing and full development branch testing.Read 4 Oct 2026 · github.com

CI integration

The project documents GitHub Actions workflows and says cargo-mutants emits structured annotations when it detects that it is running in an action.Read 5 Oct 2026 · mutants.rs

Compatibility limit

Cross-compilation is not currently supported, so the Rust tree must be buildable for the host platform.Read 4 Oct 2026 · mutants.rs

Configuration

Options can be configured in `.cargo/mutants.toml`, and the guide recommends checking that file into the source tree.Read 5 Oct 2026 · mutants.rs

Dismiss findings

Users can dismiss mutants with a `#[mutants::skip]` attribute or a configuration file.Read 4 Oct 2026 · mutants.rs

Exclude mutations

Items can be skipped with `#[mutants::skip]`, and specific mutations can be excluded with `#[mutants::exclude_re("pattern")]`.Read 5 Oct 2026 · mutants.rs

Getting started

You can run `cargo mutants` in a Rust source directory to identify functions that may be inadequately tested.Read 5 Oct 2026 · mutants.rs

How to run

Run `cargo mutants` in a Rust source directory to identify functions that may be inadequately tested.Read 4 Oct 2026 · mutants.rs

Installation

The guide documents installation with `cargo install --locked cargo-mutants`, `cargo binstall`, or binaries from GitHub releases.Read 5 Oct 2026 · mutants.rs

License and warranty

The project is MIT licensed and provided as-is with no warranty of any kind.Read 4 Oct 2026 · github.com

Maintenance

The repository describes the project as semi-actively maintained in spare time as of August 2026, with bug reports and pull requests read at higher latency.Read 4 Oct 2026 · github.com

Platform limit

Cross-compilation is not currently supported; the source tree must be buildable for the host platform.Read 5 Oct 2026 · mutants.rs

Reproducibility

Results should be reproducible when the build and test suite are deterministic.Read 4 Oct 2026 · mutants.rs

Runtime

A run’s duration depends roughly on the number of viable mutations multiplied by the time to run the test suite for each mutation.Read 5 Oct 2026 · mutants.rs

Rust versions

Building cargo-mutants requires a reasonably recent stable, nightly, or beta Rust toolchain.Read 4 Oct 2026 · mutants.rs

Setup

The tool requires no changes to the source tree or other setup before installation and use.Read 4 Oct 2026 · mutants.rs

Test requirements

Useful results require reliable, non-flaky tests that run under `cargo test` or `cargo nextest`.Read 5 Oct 2026 · mutants.rs

Test runners

Useful results require reliable, non-flaky tests that run under `cargo test` or `cargo nextest`.Read 4 Oct 2026 · mutants.rs

Where Specifiction places it

• Mutation Testing Tools#12 of 257.5