Mutatest vs Muter

Mutatest is a free command-line tool for Python projects that checks whether tests catch small changes to code. It creates valid mutations from Python’s Abstract Syntax Tree grammar and applies them to local __pycache__ files rather than changing source files. If coverage data is available, it can limit targets to lines marked as covered. Mutations are sampled randomly, with a seed available to make runs reproducible. Command-line controls include run modes, mutation categories, file exclusions, timeouts, reports, and thresholds for surviving mutants; an API supports custom controls. The documentation describes using test commands such as pytest and coverage data to filter targets. Mutatest can raise an exception when surviving mutants meet a configured threshold, including in automated runs such as CI. It supports Linux, macOS, and Windows, and is free under the MIT License. Installation requires Python 3.7 or 3.8; multiprocessing is available on 3.8, but not 3.7. Repeated test runs can be slow, so it is intended for diagnostics rather than every commit across an entire codebase.

Muter is a free, open-source mutation testing utility for Swift test suites on macOS. It changes code in a complete copy of the codebase, leaving the original untouched, then reports mutation scores for the full suite and individual files. Runs can happen in Xcode, from the command line or incrementally in continuous integration. Configuration covers Xcode projects, workspaces and Swift Package Manager. Reports can be plain text, JSON, HTML or Xcode issue navigator results, including surviving mutants. Documented operators replace relational operators, remove side effects, change logical connectors and swap ternary expressions. Muter supports projects tested with xcodebuild, including iOS, macOS, tvOS and watchOS applications, but the utility runs only on macOS 10.15 or newer. It supports Swift, not Objective-C. Any test target or suite can be used with Swift application code, although UI tests may take a long time. The project states that it has no network access and collects no analytics.