A clear description of the problem, but one-shot.

Something along the lines of

Can you generate 8-bit AVR assembly code to multiply two 24 bit posit numbers

You get some pretty funny results from the models that have no idea what a posit is. It's usually pretty clear to tell if they know what they are supposed to be doing. I haven't had a success yet (haven't tried for a while though). Some of them have come pretty close, but usually it's the trying to squeeze more than 8 bits of data into a register is what brings them down.