Generative testing is just one application of Clojure.spec. It does more than just aid in testing. It doubles as a runtime contract system, a data coercion system, and some folks are using it for compile-time checks as well (not in the testing sense, though I haven't read up on how they are doing that).

It is not a proof-like system, but outside of dependent typing, static typing does not catch value-related bugs, but Clojure.spec can. In a static type system, how easily would it be to exactly specify and guarantee that a function's second parameter is of a higher value than its first, or that a function's output is an integer between 5 and 50, etc? Clojure.spec is just predicate functions composed together to define the flow of data in a program, and those compositions can be used in a variety of ways.