Test vector chains for increased targeted and untargeted fault coverage

We introduce the concept of test vector chains, which allows us to obtain new test vectors from existing ones through single-bit changes without any test generation effort. We demonstrate that a test set T ₀ has a significant number of test vector chains that are effective in increasing the numbers of detections of target faults, i.e., faults targeted during the generation of T ₀, as well as untargeted faults, i.e., faults that were not targeted during the generation of T ₀.