1. A method comprising: generating a stimulus signal set to be supplied, as input, to first circuitry, each respective stimulus signal comprised in the stimulus signal set being generated based at least in part upon a respective non-null subset of an input signal set, no two respective stimulus signals comprised in the stimulus signal set being generated based upon the same respective non-null subset of the input signal set, the stimulus signal set comprising a respective number of stimulus signals that is greater than a respective number of input signals comprised in the input signal set.