1. A method for production testing of complex integrated circuit devices and producing data for diagnosing faults in those devices failing the production test, comprising the steps of; (a) applying a repetitive succession of structured input stimuli to the device under test, (b) processing the output responses of the device under test to the succession of input responses to produce a signature which is a predetermined function of the said output responses, (c) comparing the thus-derived signature with a signature for a known good device, (d) repeating the test procedure and input stimuli to produce a detailed data base on a device whose test signature fails to compare with the good signature, by (1) partitioning the prior test procedure into small segments of the prior test procedure, (2) deriving for each such segment a signature manifestive of the test results of each such segment, (3) comparing the thus-derived segment signature with a segment signature for a known good device, (4) repeating the segment test procedure for any test segment whose segment signature fails to compare with the known good segment signature, and (5) recording each individual set of individual input stimuli and each of the respective resultant output responses thereto to produce a detailed data base for subsequent diagnosis of the failure made of the device wherein each of the segments comprises only a fraction of the initial test procedure.