mutation-testing

Mutation testing measures test quality by introducing code mutations and running your test suite to calculate a kill rate—the percentage of mutations your tests catch. A higher kill rate indicates stronger tests that detect more potential bugs.

Install Stryker and run `npx stryker run` to execute mutation testing on your project. Stryker integrates with Jest and other frameworks to mutate your code, execute tests, and generate a mutation score report showing which mutants survived.

A low mutation score indicates that many code mutations survived your test suite, meaning your tests miss edge cases and potential bugs. Surviving mutants highlight weak test coverage on critical paths that need strengthened assertions.

Yes. Mutation testing identifies surviving mutants—code changes your tests don't catch—and guides you to write focused tests targeting those gaps. This prioritizes test generation on the weakest, most vulnerable parts of your codebase.

Yes. Stryker integrates seamlessly with Jest, allowing you to run mutation testing on your existing Jest test suite without changing your test framework or configuration.