Stryker Mutator

Stryker Mutator is a mutation testing framework that measures the effectiveness of a test suite by introducing small changes (mutants) into the code and checking whether the tests detect them. It supports JavaScript and TypeScript (StrykerJS), C# (Stryker.NET) and Scala (Stryker4s).

Stryker supports more than 30 kinds of mutations, uses code analysis and parallel test runner processes to speed up runs, and works with the user’s preferred test runner. Its reports highlight surviving mutants to help improve tests.

Stryker is open source and maintained by its community on GitHub; StrykerJS is distributed under the Apache License 2.0, with version 10.0.0 released in August 2026.