muttest-rs vs pytest-gremlins
muttest-rs
github.compytest-gremlins
github.comSide by side
| Figure | muttest-rs | pytest-gremlins |
|---|---|---|
| Price from | — | Free |
| Free plan | — | Yes |
| Free trial | — | — |
| Open source | — | — |
| Linux | — | Yes |
| Plans published | 0 | 1 |
| Spec score · Mutation Testing Tools | 6.5 (#25) | 7.7 (#10) |
| Installation | The README instructs users to install the `cargo-muttest` Cargo plugin and add `muttest` to their crate. | The project documents installation with pip, uv, and Poetry. |
| License | The repository includes an MIT license that permits use, copying, modification, distribution, sublicensing, and sale subject to its terms. | The project is MIT licensed. |
| Purpose | muttest-rs is a Rust mutation testing tool for evaluating whether a test suite catches simulated bugs. | pytest-gremlins is a pytest plugin that injects small code mutations and checks whether tests catch them. |
| Reports | The tool writes a JSON report to `target/muttest/report.json`. | It supports console, HTML, and JSON reports, including multiple report formats in one run. |
Plans
In their own words
pytest-gremlins
pytest-gremlins is a pytest plugin for checking whether an existing test suite catches small changes to code. It runs mutation tests against Python projects and can report results in the console, HTML, or JSON, including multiple formats in one run. Getting started requires Python 3.11 or later, pytest 7.0 or later, and existing tests; installation is documented with pip, uv, and Poetry. The project’s quick-start command is `pytest --gremlins`. To manage execution, it uses mutation switching, coverage-guided test selection, incremental analysis, and parallel execution, and it works with pytest-xdist. Options can be set in `pyproject.toml` or with command-line flags, while inline pragmas can pardon specific mutations. A GitHub Action can run the checks and fail a workflow if its score misses a threshold; CI examples also cover GitLab CI, CircleCI, and Dagger. It is a free, MIT-licensed package for Linux, classified as Alpha. The guide warns that an initial run may take 10–100 times as long as a normal test run, though caching can shorten later runs. It also notes that equivalent mutations can make a perfect score unattainable and unnecessary.