In the first part, the paper presents a test calculation principlewhich serves for producing tests of logic faults in digital circuits. The name of the principle is composite justification. The considered faultmodel includes stuck-at-0/1 logic faults. Both single and multiple faults are included. In this paper only combinational logic is taken into consideration. The computations are performed at the gate level. The calculation principle is comparatively simple. It is based only on successive linevalue justification, and it yields an opportunity to be realized by an efficient computer program. The first part serves for presenting the basic principle which is used in the second part of the paper. The second part deals with another fault class, namely, short-circuit or bridging faults. A short circuit is an erroneous galvanic connection between two circuit lines. Here, a new algorithm is presented for generating tests, where the composite justification is extended to handle this type of faults, as well. © Springer International Publishing Switzerland 2014.