Problem
One of the goals of test.check is for users to be able to write arbitrarily rich generators while maintaining determinism, which has obvious benefits for reproducing failures.
Currently the {{fspec}} generator generates a function which itself generates random return values by calling {{clojure.test.check.generators/generate}}, which is a function intended only for development use as it circumvents test.check's controlled source of psuedorandomness. It also circumvents test.check's sizing mechanism, since the {{generate}} function always uses a size of {{30}}.
Possible Solutions
I see two reasonable solutions to this, depending on whether the generated function ought to be a pure function (which it currently isn't, since it ignores its arguments and randomly generates a return value).
Pure Function
We can generate a non-empty vector of possible return values and use that to create a function that selects one of the possible return values using the {{hash}} of the arguments.
Impure Function
We can generate a non-empty collection of possible return values and use that to create a function with internal state that cycles through the possible return values.
