Side by side
mutator vs pytest-gremlins
Both stand on mutation testing tools. Which one you can start free with, which one lets you read the code, and what each costs once you pay.
Free plan Linux
mutator offers mutation testing for R packages, including CI support and controls for test execution. Developers using the generic installed-tests fallback should account for its full-suite run instead of coverage-guided selection.
Visit mutator Free plan Linux
pytest-gremlins adds mutation testing to existing pytest suites, with reporting and CI options. Allow for a potentially much longer first run, and do not treat a 100% mutation score as a necessary target: equivalent mutations can make it unattainable.
Visit pytest-gremlinsThe facts
| mutator | pytest-gremlins | |
|---|---|---|
| Free plan | Yes | Yes |
| Open source | Not published | Not published |
| Runs on | Linux | Linux |
| Lowest paid plan | Not published | Free or on request |
| Plans published | None | 1 |
| Maker | Not published | Not published |
| Website | pdonatbouillud.com | github.com |
| On mutation testing tools | #17 of 25 | #21 of 25 |
mutator: what it does well
- Reports a mutation score and surviving mutants
- Supports testthat and tinytest
- Runs tests in parallel
- Includes a reusable GitHub Actions workflow
- Users can cap mutants and override timeouts
What to know first
- Generic installed-tests fallback runs the full suite
- Coverage-guided selection is unavailable for the generic fallback
- Equivalent-mutant detection uses an OpenAI-compatible API
pytest-gremlins: what it does well
- Free, MIT-licensed package.
- Supports incremental analysis and parallel execution.
- Offers console, HTML, and JSON reports.
- GitHub Action can enforce a mutation-score threshold.
What to know first
- Requires Python 3.11 or later and pytest 7.0 or later.
- A first run may take 10–100 times as long as normal tests.
- Development status is classified as Alpha.
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