A circuit arrangement comprising a logic circuit to be tested and a test circuit. The logic circuit comprising logic-circuit-internal combinations configured to generate output data from input data based on a predetermined relationship. The logic circuit is configured to detect whether the relationship is satisfied and to provide an error signal if the relationship is not satisfied. The test circuit is configured to alter logic-circuit-internal combinations, to detect the error signal, and to output an alarm signal if the error signal is not detected upon alteration of the logic-circuit-internal combinations.