A novel approach for testing and diagnosing of multiple faults is discussed. A definition of a test group is introdueed to eope with the problem of fault masking. The eonditions are introduced to prove that a test group is sufficient to avoid fault masking. A method is presented for generating test groups regarding fault masking. Unlike the traditional test approaches, we do not target the faults as test objectives. The goal is to verify the correctness of a part of the circuit. The whole test sequence is presented as a set of test groups where each group has the goal to identify the correctness of a selected part of a circuit. The method facilitates fault diagnosis in the presence of multiple faults. Experimental research investigates the feasibility of the method and shows a way for tradeoffs between the test cost and robustness of the test regarding multiple faults.