1. A method for checking conformance of a digital circuit design with a given set of testability design rules, comprising the steps of: building a circuit description of the digital circuit design to be checked using a circuit description language that permits use of a user defined, non-standard logic; providing a circuit dependent sequence of stimuli using said circuit description language; providing a simulator which builds up a simulation model when said circuit description is loaded into it; applying the stimuli to the circuit description by loading the circuit description and the stimuli into the simulator and allowing the simulator to process the stimuli as applied to the circuit description until the simulator has no more events to process; and switching the simulator model into a check mode in which each component of the circuit checks a testability state and issues error messages if an illegal state was found.