"DFY and DFR are more important than DFT"

The purpose of testing a circuit is to verify that it functionally matches its ideal behavior. If the behavior is not what is anticipated, it is considered failing. If the failing behavior is a result of a defective design, e.g. a “bug”, a serious re-design effort would be undertaken. This re-design is based upon knowledge of typical circuit behavior and re-design encompasses using a broad spectrum of electrical modeling. However, this only looks into one aspect of a circuit: the electrical representation. This effort does not necessarily explore the physical manifestation of the components used to create the circuit and their susceptibility to failure.