mutation-testing

Mutation testing improves Rust test suites by introducing semantic mutants into the code and checking if tests fail. Surviving mutants reveal test adequacy gaps, enabling targeted improvements to your test coverage.

Yes, you can run cargo-mutants on a specific package or use incremental diff-based analysis. This targeted mutation testing speeds up feedback and focuses triage on changed code rather than the full workspace.

You triage surviving mutants by reading structured results from target/mutants-output. This output identifies which semantic mutants bypassed your tests, guiding you to prioritize and write the specific test improvements needed.

Yes, the workflow reads mutants.toml for configuration. This file configures how cargo-mutants operates across your Rust workspace, ensuring the semantic mutants are introduced and evaluated according to your project settings.

Measuring test adequacy in Rust is best done by injecting small semantic changes and evaluating test failures. This approach reveals whether your tests actually catch logic errors, providing a deeper assessment than line coverage.

Tests pass despite logic changes because of test adequacy gaps, where surviving mutants indicate missing assertions. Running mutation testing identifies these exact weaknesses so you can add the necessary test cases.