lucascs@protonmail.com Lucas C.S. cargo-mutants performs mutation testing: it rewrites your source in small, plausible ways -- a returned value replaced, a condition negated -- and reruns the test suite for each mutant. A mutant that survives is a change no test noticed, which is a far stronger signal than line coverage: coverage says a line ran, a surviving mutant says nothing checked what that line did. https://github.com/sourcefrog/cargo-mutants/issues sourcefrog/cargo-mutants