I asked once about making Smith.constructInput() pub so that it could be used for simple fabrication of input data, as you see a lot of in the fuzz source test blocks, but I haven’t taken it further (I haven’t created an issue or PR to that effect). If I’m reading your request correctly, this is the kind of thing you’d like. However, it could be that you’re trying regular unit testing, rather than fuzz testing, if you feel that specific values are important. The other way to constrain certain data is to use weights. Look above, in this thread, for the great example of a network packet processor in which a checksum field. Obviously, if all fields were random, then the chances of a random checksum matching would be quite astronomical. In this case, the pattern of requesting a (random) bool from the Smith; if true, calculate the checksum correctly so that the “good path” in the code will be taken. If false, allow a random value, in order to make sure the “error path” behaves well. You could add weights to indicate you’d like the correct path taken 80% of the time. If your numbers “42” and “53” are so specific, you could theoretically fabricate a request for a “random” int via .rangeAtMost() to constrain it to only individual values, but I’ve never tried that.