Circuit fault diagnosis

Our electronic circuit (and component) models (be they in the form of equivalent circuits, characteristic curves, etc.) are models of how correct circuits operate when assembled out of "on spec." component parts.  These models do not, in general, tell us much of what faulty components will do or how incorrectly wired circuits will behave.  Some simple fault models can be added to our circuit models ( see, for example, Simply Logical, by Peter Flach, Wiley and Sons, 1994, pgs 163-166 and Digital Systems, 5 th edition, R. J. Tocci, Prentice-Hall, 1991, pgs 130-139) But we typically can't anticipate all possible fault mechanisms.