Definitions of the numbers of detections of target faults and their effectiveness in guiding test generation for high defect coverage

The number of times a fault f in a combinational circuit is detected by a given test set T was shown earlier to affect the defect coverage of the test set. The earlier definition counted each test in T, that detects f, as a distinct detection of f. This definition counts two tests as distinct detections even if they differ only in the values of inputs that do not affect the activation or propagation of the fault. In this work, we introduce a stricter definition that requires that two counted tests would be different in the way they activate and/or propagate the fault. We describe procedures for constructing test sets based on the stricter definition, and compare them to test sets for the earlier, less strict definition. The results show a simple criterion to decide when it may be necessary to combine the two definitions in order to obtain a high quality test set