You're supposed to use it as a repl, so you start with a test for `fib(1) = 1`, then `fib(2)` and so on. Once you're confident of your implementation, you use q

You're supposed to use it as a repl, so you start with a test for `fib(1) = 1`, then `fib(2)` and so on. Once you're confident of your implementation, you use quickcheck to test general properties of the system. Similarly if you find a bug in the live system, you add a test for that and the initial output will be wrong. Then you fix your code until it prints the correct value and commit that so any regression will be caught.