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Coverage-guided fuzzing is a testing technique that monitors code coverage during execution to generate new inputs targeting untested paths. It repeatedly mutates inputs to maximize coverage, automatically discovering hard-to-reach crashes and undefined behavior in Ruby code and native C extensions.

Yes, you can use libFuzzer and ASAN integrations to fuzz pure Ruby code. The approach provides distinct harness support for pure Ruby targets and native extensions, allowing you to systematically surface memory errors and stability issues across both environments.

To set up a fuzzing harness for a Ruby gem with native C bindings, you need to load the gem and define a target function that accepts fuzz inputs. You can then execute the provided harness to feed mutated data into your library code and monitor for crashes.

Coverage-guided fuzzing monitors code execution paths to generate inputs that reach untested code branches. It systematically mutates data to maximize coverage, automatically discovering hard-to-reproduce memory errors and undefined behavior in Ruby applications and native C extensions.

The best way to uncover hard-to-reproduce memory errors in Ruby gems is through coverage-guided fuzzing with sanitizer integrations. This approach systematically mutates inputs to surface crashes and undefined behavior that manual testing rarely reaches.