Editing Fault model (section)

===Equivalence collapsing===
It is possible that two or more faults produce same faulty behavior for all input patterns. These faults are called equivalent faults. Any single fault from the set of equivalent faults can represent the whole set. In this case, much less than k×n fault tests are required for a circuit with n signal line. removing equivalent faults from entire set of faults is called fault collapsing. fault collapsing significantly decreases the number of faults to check.


In the example diagram, red faults are equivalent to the faults that being pointed to with the arrows, so those red faults can be removed from the circuit. In this case, the fault collapse ratio is 12/20.