How effective is property based testing in practice? I would assume it has no trouble uncovering things like missing null checks or an inverted condition because you can cover edge cases like null, -1, 0, 1, 2^n - 1 with relatively few test cases and exhaustively test booleans. But beyond that, if I have a handful of integers, dates, or strings, then the state space is just enormous and it seems all but impossible to me that blindly trying random inputs will ever find any interesting input. If I have a condition like (state == "disallowed") or (limit == 4096) when it should have been 4095, what are the odds that a random input will ever pass this condition and test the code behind it?

Microsoft had a remotely similar tool named Pex [1] but instead of randomly generating inputs, it instrumented the code to enable executing the code also symbolically and then used their Z3 theorem proofer to systematically find inputs to make all encountered conditions either true or false and with that incrementally explore all possible execution paths. If I remember correctly, it then generated a unit test for each discovered input with the corresponding output and you could then judge if the output is what you expected.

[1] https://www.microsoft.com/en-us/research/publication/pex-whi...