On avoiding undetectable faults during test generation

We use a property that distinguishes most of the undetectable faults in a circuit from detectable ones, in order to avoid targeting undetectable faults during test generation. We show that it is possible to avoid most of the undetectable faults until most of the detectable faults are detected. The test generation process is speeded-up by avoiding undetectable faults, since wasted effort expended in trying to detect undetectable faults is avoided. When all or most of the faults that remain undetected by the test generator appear to be undetectable faults, a procedure for identifying undetectable faults may be used. Detectable faults, if any such faults remain, may then be given to the test generator to obtain complete fault coverage. We study the proposed property in conjunction with test generation processes for both combinational and sequential circuits.