One of the things that became a source of frustration is writing the specs that define the shape of the inputs.
Does FuzzBuzz make that any easier?
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)
So you can do: auto s = datasource.Get<std::string>();
For each type I need I override Get<T> for that type. If the data source class is out of data, I throw a specific exception, that I catch at the global level. This works like a breeze and the advantage over protobufs is that it's faster (no Protobuf parsing overhead, errors) and you never consume more than you need.