mutation-test

Mutation testing identifies weak tests by deliberately introducing small code changes, called mutants, into the codebase. If the existing test suite passes despite these mutants, the tests are not robust enough to catch actual bugs, exposing a false sense of security.

High code coverage only guarantees that code is executed during testing, not that assertions are robust. Mutation testing addresses this by modifying the code to ensure tests actually fail when bugs are introduced, revealing insufficient or brittle tests.

You can execute mutation testing on your current project by applying tools like Stryker, PITest, or mutmut to generate code mutants. The tool runs your test suite against these mutants and analyzes the failure rates to pinpoint specific weak tests.

Yes, mutation testing applies directly to software development projects requiring rigorous quality assurance. It integrates into your workflow to validate the effectiveness of existing test suites without requiring external dependencies.

A mutation score quantifies the percentage of introduced code mutants that your test suite successfully detects and fails against. A lower score indicates that many edge cases and potential bugs remain untested despite high line coverage.