Finite complete suites for CSP refinement testing

In this paper, new contributions for model-based testing using Communicating Sequential Processes (CSP) are presented. For a finite non-terminating CSP process representing the reference model, finite test suites for checking the conformance relations traces and failures refinement are presented, and their completeness (that is, capability to uncover conformity violations) is proven. The fault domains for which complete failure detection can be guaranteed are specified by means of normalised transition graphs representing the failures semantics of finite-state CSP processes. While complete test suites for CSP processes have been previously investigated by several authors, a sufficient condition for their finiteness is presented here for the first time. Moreover, it is shown that the test suites are optimal in two aspects: (a) the maximal length of test traces cannot be further reduced, and (b) the nondeterministic behaviour cannot be tested with smaller or fewer sets of events, without losing the test suite's completeness property. (C) 2019 Elsevier B.V. All rights reserved.