This paper presents a nonenumerative automatic test pattern generator for r
obustly testable path delay faults. In contrast to earlier work [26], the p
attern generator takes into consideration the conditions for robust propaga
tion while sensitizing sets of paths. This increases the probability of tes
ting them robustly with a single test. Novel algorithms are described which
identify sets that contain many such potentially compatible paths. The num
ber of detected faults is estimated using a simple and fast method. The app
roach compares favorably to [26] in both fault detection and time performan
ce.