Extended selection of switching target faults in CONT algorithm for test generation

We describe an extended selection of switching target faults in the CONT algorithm. The main difficulty in test generation is the conflict that arises in the process of determining the signal values due to reconvergent fanouts. Conventional approaches for test generation change a signal value, which causes conflicts to another possible choice for backtracking. In the CONT algorithm, a strategy of switching target fault was proposed as a new backtracking mechanism. In this method, the target fault is switched to a new target fault instead of making an alternative assignment on the primary input value when a conflict occurs. A disadvantage of the CONT algorithm is that unjustified lines exist in the process of test generation. These unjustified lines make the procedure of switching targets complicated and restrict the possible choice in selecting the new target fault. In the new version of CONT, called CONT-2, we have removed the unjustified lines in the process of test generation and have extended to two target-fault types for switching targets. Implementing CONT-2 by a Fortran program, ISCAS85 benchmark circuits are examined. Experiments on a combined system with fault simulation followed by CONT-2 are also presented.