1. A method for applying external clock and data patterns for logic built-in self testing (“LBIST”) in a simulator, comprising: setting up a simulation model in the simulator for a logic under test; setting up an external LBIST block in the simulation model, wherein the external LBIST block comprises pre-verified internal clock and data pattern logic; connecting external clock inputs and external data inputs from the external LBIST block to the logic under test; determining external clock patterns and external data patterns to test the logic under test; applying the external clock and data patterns to the logic under test; and receiving and processing output patterns from the logic under test.