Towards a Family of Test Selection Criteria for Symbolic Models of Real-Time Systems

Abstract

In model-based testing, test cases are generated from a specification model. To avoid an exhaustive search for all possible test cases that can be obtained, usually an expensive and infeasible activity, test case generation may be guided by a test selection criterion. The objective of a test selection criterion is to produce a minimal test suite and yet effective to reveal faults. However, the choice of a criterion is not straightforward specially for real-time systems, because most criteria presented in the literature are general-purpose. Moreover, the relationship between general-purpose and specific criteria for real-time systems is not clear. In this paper, we investigate the criteria that can be applied for test case generation in the scope of model-based testing of real-time systems, specifically of Timed Input-Output Symbolic Transition Systems (TIOSTS) models. We formalize a family of 19 test selection criteria ordered by strict inclusion relation for TIOSTS models. The family combines general-purpose data-flow-oriented and transition-based criteria with specific reactive and real-time systems criteria. We also perform an empirical study to compare the effectiveness of selected criteria. Results of the empirical study indicate that failure detection capability of the generated test suite may vary, but differences are not significant for time failures. We conclude that more effective criteria for the model-based testing of real-time systems are still needed.