That's a problem that we've been thinking about a lot. The way our fuzzing works right now is that your method consumes an array of bytes, which you can then use to build up arbitrary structures. It's simple, but manages to be really generic and flexible at the same time. Of course, it means you do have to define what your inputs look like.

We do have plans to build some tools to make this easier. I'd like to see a scenario where defining inputs is as simple as specifying the data types that your code requires. (Or perhaps even automatic detection, for less complex cases)