mutation-testing

Mutation testing reveals weak tests by systematically applying mutation operators to source code and running the test suite. If a mutated code version survives without failing any tests, it exposes a gap in test effectiveness and coverage.

Run mutation testing during code changes, PR reviews, and post-refactor verification. It surfaces fragile tests and missing checks precisely when code is modified, guiding test improvements before integration into CI pipelines.

Select your target project, configure mutation settings, and run your existing test suite. The workflow applies mutation operators to the code, executes the tests, and generates a report showing killed versus survived mutants for review.

Test coverage measures which code lines execute during tests, while mutation testing measures test effectiveness by mutating code to see if tests actually catch bugs. Mutation testing identifies surviving mutants that coverage metrics miss.

Yes, mutation testing is specifically applicable during PR reviews. It runs your test suite against mutated source code to surface gaps in test coverage, providing a concise results summary of killed and survived mutants to guide improvements.

Killed mutants are code mutations that caused tests to fail, indicating effective tests. Survived mutants are mutations that did not trigger test failures, revealing weak tests that fail to catch specific code changes and require adjustment.