1. A method comprising: for each of a plurality of faults, determining, by one or more computing devices, a plurality of probability values associated with observing a fault along a plurality of propagation paths of a circuit design; generating, by the one or more computing devices, a plurality of residual test cubes by at least, for each of the plurality of faults, generating a corresponding residual test cube for the fault based on determining that one or more from the plurality of probability values are above a predefined threshold; and generating, by the one or more computing devices, test templates based on merging the plurality of residual test cubes.