I think that fuzz testing is best described in the context of two other types of tests that go beyond "traditional" unit/integration tests: property and mutatio

I think that fuzz testing is best described in the context of two other types of tests that go beyond "traditional" unit/integration tests: property and mutation testing. The three complement each other so well in ways that are hard to describe without trying them yourself. Quickcheck is a property tester, which essentially can be thought of as a "bytecode fuzzer that also happens to check for correct behavior". It uses an algorithm to generate arbitrary inputs that satisfy a set of constraints, and then ensures that the outputs demonstrate a property of the function being fulfilled. Think about mathematical properties of functions or the lack thereof: commutativity, associativity, and even properties of linear relations you might remember from Linear Algebra. Values that violate the expected properties are saved; you can build unit tests that check these values later or cache them for future runs. Fuzzing is a form of black-box testing that repeatedly runs software differently and tries to crash it. Causes and behavior of crashes can later be inspected. Mutation testing alters every statement in your code one at a time to change its behavior. Each alteration is a "mutant". If an alteration does not cause one of your tests to fail, the mutant has not been "killed". Your goal is to have a good kill ratio. This is a far better metric for test effectiveness and dead code elimination than statement/branch coverage. Property testing is kind of like a bytecode fuzzer and mutation testing is very much like a fuzzer for your tests. But property testing is a white-box form of testing with good knowledge of your code; I'd consuder mutation testing to be "grey-box" testing of your test code. "True" fuzz testing is as black-box as you can get: just let an algorithm run your program for a long time (anywhere from hours to months) to find subtle bugs (crashes and other black-box failures) at scales humans struggle with. In conclusion: Yo dawg, I heard you like tests. So I fuzzed the mutation tests on your property tests to see if arbitrary input on arbitrary code produced arbitrary output without arbitrary exits.