PBT testing and fuzzing are basically the same thing in my mind.

What's funny though is that the reasoning needed to say some sampling is comprehensive....makes it closer fo proofs! AFL — coverage-based fuzzing — was the original innovator here, but imagine an interpreter — code coverage in the interpreter itself isn't so good, you also want to explore the interpreted program!

This is why "is my testing comprehensive?" is actually an open-ended problem that, in the limit, is just as hard as formal verification.

I suspect we're basically going to see a convergence here. Randomized testing can be called "Monte Carlo formal verification" hehe.