It is common to see software testing experiments where a benchmark program is seeded with N benchmark mutations, then declared to have N faults. We argue that in the absence of a formal definition of what is a fault, let alone what are N faults, it is difficult to assign a meaning to such claims. We further argue that in order to assign a meaning to a claim such as “Program P has N faults”, we need to define what is a fault, and what is a unitary fault; also we find that such a claim depends on a number of parameters that must be made explicit for the claim to be meaningful. Finally, we propose a set of metrics that reflect program faultiness, and contrast them to current practice, using the tcas component of the Siemens benchmark as an illustrative example.