Mutatest vs Stryker Mutator

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.

Stryker Mutator is mutation-testing software for JavaScript, TypeScript, C#, and Scala. It changes source code in more than 30 defined ways, then runs unit tests against those variants to show how effectively the tests detect faults. The project supports incremental analysis, parallel execution, surviving-mutant reports, and mutation quality gates. It is test-runner agnostic, with listed integrations including Cucumber, Jasmine, Jest, Karma, Mocha, Tap, Vitest, and a command runner. Code analysis and parallel test-runner processes are used to speed runs, although the FAQ notes that mutation jobs can be slow and recommends improving unit-test performance or limiting files. Stryker is free, released under Apache 2.0, and available through API or self-hosted use. Its cloud dashboard stores reports and mutation-score badges, free for open source, with GitHub account setup and github.com as the supported Git provider. Reports can be sent directly or by HTTP PUT with an API key.