[josephg]

Yeah I do this kind of fuzz testing all the time. Its an incredible way to test code.

For fuzz testing I go even further with asserts. I usually also write a function called dbg_check(), which actively goes through all internal data and checks that all the internal invariants hold. Eg, in a b-tree, the depth should be the same for all children, children should be in order, width of all nodes is between n/2-n, and so on.

If anything breaks during fuzz testing (which is almost guaranteed), you want the program to crash as soon as possible - since that makes it much easier to debug. I'll wrap a lot of methods which modify the data structure in calls to dbg_check, calling it both before and after making changes. If dbg_check passes before a function runs, but fails afterwards - then I have a surefire way to narrow in on the buggy behaviour so I can fix it.