Testing data processing-oriented systems from stream X-machine models

One of the great benefits of using a stream X-machine to specify a system is its associated testing method. Under certain design for test conditions, this method produces a test suite that can determine the correctness of the implementation under test (IUT), provided that the processing functions of the stream X-machine specification have been correctly implemented. The method was originally developed for controllable stream X-machines. A recent paper generalizes the original method by considering specifications that do not meet the controllability requirement. However, it is still required that a controllable stream X-machine model of the IUT exists and the size of the test suite produced strongly depends on the (estimated) upper bound on the number of states of this controllable model. While this assumption is in general reasonable for most interactive systems, it may produce unmanageable test suites for even simple data processing-oriented applications. This paper provides a new variant of the stream X-machine based testing method that no longer depends on the size of a controllable model of the IUT. In data processing-oriented applications, the new method can drastically reduce the size of the test suite produced at the expense of a (possibly) more complex generation process.