base on :zombie: Inject bugs and see if your tests catch them! # cargo-mutants <https://github.com/sourcefrog/cargo-mutants> [](https://github.com/sourcefrog/cargo-mutants/actions/workflows/tests.yml?query=branch%3Amain) [](https://crates.io/crates/cargo-mutants) [](https://lib.rs/crates/cargo-mutants) [](https://github.com/sponsors/sourcefrog) [](https://donate.stripe.com/fZu6oH6ry9I6epVfF7dfG00) cargo-mutants helps you improve your program's quality by finding places where bugs could be inserted without causing any tests to fail. Coverage measurements can be helpful, but they really tell you what code is _reached_ by a test, and not whether the test really _checks_ anything about the behavior of the code. Mutation tests give different information, about whether the tests really check the code's behavior. The goal of cargo-mutants is to be _easy_ to run on any Rust source tree, and to tell you something _interesting_ about areas where bugs might be lurking or the tests might be insufficient. **For more background, see the [slides](https://docs.google.com/presentation/d/1YDwHz6ysRRNYRDtv80EMRAs4FQu2KKQ-IbGu2jrqswY/edit?pli=1&slide=id.g2876539b71f_0_0) and [video](https://www.youtube.com/watch?v=PjDHe-PkOy8&pp=ygUNY2FyZ28tbXV0YW50cw%3D%3D) from my Rustconf 2024 talk.** **The main documentation is the user guide at <https://mutants.rs/>.** ## Prerequisites cargo-mutants can help on trees with non-flaky tests that run under `cargo test` or [`cargo nextest run`](https://nexte.st/). ## Install ```sh cargo install --locked cargo-mutants ``` You can also install using [cargo-binstall](https://github.com/cargo-bins/cargo-binstall) or from binaries attached to GitHub releases. ## Quick start From within a Rust source directory, just run ```sh cargo mutants ``` To generate mutants in only one file: ```sh cargo mutants -f src/something.rs ``` ## Integration with CI The [manual includes instructions and examples for automatically testing mutants in CI](https://mutants.rs/ci.html), including incremental testing of pull requests and full testing of the development branch. ## Help advance cargo-mutants If you use cargo-mutants or just like the idea you can help it get better: * [Post an experience report in GitHub discussions](https://github.com/sourcefrog/cargo-mutants/discussions), saying whether it worked, failed, found interesting results, etc. * [Sponsor development](https://github.com/sponsors/sourcefrog) ## Project status As of August 2025 this is an actively-maintained spare time project. I expect to make [releases](https://github.com/sourcefrog/cargo-mutants/releases) about every one or two months. It's very usable at it is and there's room for lots more future improvement, especially in adding new types of mutation. If you try it out on your project, [I'd love to hear back in a github discussion](https://github.com/sourcefrog/cargo-mutants/discussions/categories/general) whether it worked well or what could be better: * Did it work on your tree? Did you need to set any options or do any debugging to get it working? * Did it find meaningful gaps in testing? Where there too many false positives? * What do you think would make it better or easier? This software is provided as-is with no warranty of any kind. ## Further reading See also: * [cargo-mutants manual](https://mutants.rs/) * [How cargo-mutants compares to other techniques and tools](https://github.com/sourcefrog/cargo-mutants/wiki/Compared). * [Design notes](DESIGN.md) * [Contributing](CONTRIBUTING.md) * [Release notes](NEWS.md) * [Discussions](https://github.com/sourcefrog/cargo-mutants/discussions) ", Assign "at most 3 tags" to the expected json: {"id":"13468","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"