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1.8K Stars 167 Forks Apache License 2.0 2.6K Commits 105 Opened issues


Mutation testing for JavaScript and friends

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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.

Welcome to StrykerJS's monorepo. This is where all official stryker packages are maintained. If you're new to monorepos: don't be scared. You'll find the packages in the


If you're interested in why we chose a monorepo, please read babeljs's design document about monorepos. We use it for the same reasons as they do.


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

Getting started

Please follow the quickstart on the website.

For small js projects, you can try the following command:

npm install --save-dev @stryker-mutator/core
# Only for small projects:
npx stryker run

It will run stryker with default values:

  • Uses
    npm test
    as your test command
  • Searches for files to mutate in the


$ npx stryker  [options] [configFile]

See usage on

Supported mutators

See our website for the list of currently supported mutators.


See configuration on

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