Design for testability in embedded software projects

The purpose of this white paper is to focus on design techniques or methodologies that add testability features to embedded software which is an integral and important process for verification of any safety critical system. This paper presents testability in two forms: software testability i.e. testability at code level and design testability: i.e. testability at software requirements level. The two testability forms are further classified into subtypes explained in detail with examples which cite issues that are faced by engineers while performing verification. In this paper I have also come up with metrics which could become an important criterion in calculating the testability of a system considering the number of inputs that can be driven and the outputs that can be observed in the software during the verification process. Practical usage of these metrics may help designers understand how testable the system they have designed is, thus reducing verification effort and project cost. Good testability features, if not present in a system, may lead to increased cost and completion period of the project at a time when cost reduction and deadline chasing is the key to winning future projects. This paper endeavors to provide software developers guidance to incorporate important testability features into the software during the design and coding phase.