Mutation testing for Scala. Work in progress...
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Professor X: For someone who hates mutants... you certainly keep some strange company.
William Stryker: Oh, they serve their purpose... as long as they can be controlled.

Note: this project is still very much in early development and (probably) not ready to reliably be used in large projects!

Despite that, we'd be happy to help you out if you run into any problems or have any questions 😁. In the meantime, start by mutation testing JavaScript with Stryker.


For an introduction to mutation testing and Stryker's features, see

Getting Started

Stryker4s is a mutation testing framework for Scala. It allows you to test your tests by temporarily inserting bugs.

We do not (yet) have a SBT plugin or other easy ways to run the project. However, the command test-runner should allow you to run the project with any build-tool. The easiest way to test the project right now is by cloning the repository, creating a stryker4s.conf file with a base-dir of your project and running Stryker4s with sbt run.


See for setting up your stryker4s.conf file.

Supported mutators

See for our supported mutators.


Want to contribute? That's great! Please have a look at our contributing guide.