Analyzing testability on data flow designs

High testability is a strongly desired feature of software, since it tends to make the validation phase more efficient in exposing faults during testing, and consequently it increases the quality of the end-product. Furthermore, testability is a criterion of crucial importance to software developers, since the sooner it can be estimated, the better the software architecture will be organized to improve subsequent maintenance. This paper is concerned with the testability of data flow software designs, its definition, and the axiomatization of its expected behavior. This behavior is expressed in relation to basic operations that are applicable on designs, and to the dedicated test strategies which are selected. Measurements are proposed which are consistent with the stated axioms. The whole approach is demonstrated using design specifications of embedded software developed in the avionics industry