Fault coverage
Beginner
The share of pretend flaws that the tests would catch. 99% means they catch 99 out of every 100.
Novice
The number of modeled faults the test patterns detect, divided by the total number of modeled faults. A related number, fault efficiency, leaves out faults that are proven impossible to test, so they don’t count against the patterns.
Expert
Always quote it with the fault model, the denominator, and whether the fault list is collapsed. Tools differ on names (fault coverage, test coverage, fault efficiency) and on how they credit possibly-detected faults, so read the report’s definitions.
Explained in Design for test (Design Flow).
See also: Untestable (redundant) fault, DPPM.