On the saturation of n-detection test sets with increased n

An n-detection test set contains n different tests for each target fault. The value of n is typically determined based on test set size constraints, and certain values have become standard. In this work we investigate appropriate values for n by considering the saturation of the n-detection test generation process. As n is increased, eventually the rate of increase in test set quality starts dropping. Saturation occurs when the increase in test set quality with n drops below a certain level. We introduce three parameters of an n-detection test set to measure saturation of the test generation process: (1) the fraction of faults detected n times or less by the test set, (2) the fraction of faults detected fewer than n times by the test set, and (3) the test set size relative to the size of a one-detection test set. We demonstrate that the behavior of each one of these parameters follows a unique pattern as n is increased, and certain features of this behavior can be used to identify saturation. All the parameters are easy to compute during the test generation process.