mutmut
Metrics as of , from the GitHub or GitLab API of each repository. Refreshed monthly.
What mutmut is
mutmut is a mutation testing system for Python. By default it runs pytest against the tests folder and works out which code to mutate. It remembers completed work, so an interrupted run resumes where it stopped. It picks which tests to execute for each mutant. The mutmut browse command opens a terminal UI that lists mutants and retests them. The mutmut apply command writes a chosen mutant to disk. Settings go in setup.cfg or a tool.mutmut section of pyproject.toml. Optional filters restrict mutation to lines covered by coverage.py or drop mutants that mypy or pyrefly reject. It requires a system with fork support, so Windows use goes through WSL.
Written from the project's README, read .
- Category
- Code quality and static analysis
- License
- BSD-3-Clause
- Language
- Python
- Changelog
- Releases on GitHub
Repository metrics
Status
activeLast commit within 90 days of the fetch date.Computed from the last commit date and the archive flag on the fetch date. See the status rules.
Alternatives
Listed code quality and static analysis tools, same primary language first, then by GitHub stars. Each line gives one fact from the tool's documentation where it differs from mutmut's, with its source.
mypy: Languages or files analysed: Python programs with type hints. source: README
Bandit: Languages or files analysed: Python files, parsed into an abstract syntax tree (AST). source: README
Pylint: Languages or files analysed: Python code (latest version supports Python 3.10.0 and above). source: README
Flake8: Languages or files analysed: Python code, through PyFlakes, pycodestyle and the McCabe script. source: README
Ruff: Languages or files analysed: Python files (*.py, *.pyi), Jupyter Notebooks (*.ipynb) and pyproject.toml. source: Docs: Configuring Ruff
ShellCheck: Languages or files analysed: Shell scripts in the sh, bash, dash, ksh and BusyBox dialects. source: Docs: shellcheck(1) manual
ESLint: Languages or files analysed: ECMAScript/JavaScript code; JSX parsing when enabled. source: README
golangci-lint: Languages or files analysed: Go code. source: README
How to install
pip install mutmutQuestions
Is mutmut open source?
Yes. mutmut is released under BSD-3-Clause, an OSI-approved license, as reported by the GitHub API on 2026-09-22.
Is mutmut maintained?
On 2026-09-22, the last commit to the default branch was on 2026-09-12, so the listed status is active. Rule: Last commit within 90 days of the fetch date.
How many GitHub stars does mutmut have?
1,448 stars on 2026-09-22, from the GitHub API. The number is refreshed at each monthly update.
What language is mutmut written in?
The repository's primary language, as reported by the GitHub API, is Python.
How do I install mutmut?
The README gives this command: pip install mutmut
Sources
- GitHub REST API: repository, read
- GitHub REST API: commits, read
- GitHub REST API: latest release, read
- GitHub REST API: contributors, read
- README, read