Mutant vs MutPy

Mutant is Ruby mutation-testing software that changes code in controlled ways to check whether tests catch the changes. It alters arithmetic, logical and bitwise operators, removes statements, and changes return values. It works with RSpec, Minitest and Test::Unit, and supports incremental runs for CI. Supported Ruby versions are 3.2, 3.3, 3.4 and 4.0 for runtime, syntax and mutations. Rails support is verified for versions 7.2, 8.0 and 8.1, with parallel-worker database isolation for PostgreSQL and SQLite. Mutant runs on developers’ machines or in CI, and includes parallel execution and reports of surviving mutants. It cannot generate mutations for methods defined inside closures, including methods created with module_eval, class_eval, define_method or define_singleton_method. The open-source plan is free for public repositories with the full feature set. Commercial monthly pricing is $30 a month per developer; yearly pricing is $250 a year per developer. CI use requires no additional subscriptions.

MutPy is a mutation testing tool for Python that checks whether a test suite catches changes to its source code. It creates mutations at the abstract syntax tree level, then runs tests to reveal which changes go undetected. The project describes compatibility with Python 3.3 and later. It uses unittest by default, while pytest support is experimental. Reports can be generated in YAML or HTML, and coverage analysis can restrict mutation to code exercised by tests. Users can also select or disable operators and sample a percentage of mutants. MutPy supports higher order mutations and includes standard and experimental operator sets. Installation is documented through pip from PyPI or from the repository source. The software is free at free and licensed under Apache License 2.0. PyPI lists version 0.6.1, released November 17, 2019, as the latest release. The README warns that disabling stdout can damage tests that interact with sys.stdout.