Gremlins

Gremlins is a mutation testing tool for Go. It is designed to work well on small Go modules, such as microservices, where it helps validate the tests, supports test-driven development and can be used as a quality gate in CI.

Gremlins uses the coverage of the test suite to mutate only the covered code, then runs the tests for each mutant and reports which mutants were killed, which survived and which were not covered. Thresholds on efficacy and mutant coverage can fail the build. Its authors note that runs on very large modules can take hours.

Gremlins is free and open source under the Apache 2.0 licence. It is still in its 0.x releases.