Mutation Testing with Stryker

Find gaps in your test suite using mutation testing with Stryker. Introduces deliberate code mutations and reports which ones your tests fail to catch, revealing undertested code paths.

This skill runs Stryker Mutator against your codebase to evaluate test suite quality. It introduces code mutations (changing operators, removing conditionals, altering return values), runs your tests against each mutation, and reports which mutations survive — indicating weak test coverage in critical areas.

When to use

Use when you want to verify your test suite actually catches bugs, before major refactors to ensure safety, or to identify which code paths need more thorough testing.

Examples

Audit test quality

Run mutation testing to find weak spots in your test suite

Run mutation testing on our payment module — I want to know which critical paths our tests don't actually protect

Write tests for surviving mutants

Generate tests to kill surviving mutations

Stryker found 23 surviving mutants in the auth module — write tests that catch each of these mutations