On the influence of test adequacy criteria on test suite reduction for model-based testing of real-time systems.

Abstract

Model-based testing is a testing approach that relies on the existence of abstract models of an application to generate, execute and evaluate tests. Test case generation plays an important role in model-based testing. Since it consists of a systematic search for test cases that can be extracted from models, model-based testing usually generates large test suites which are too expensive to execute in full. Test suite reduction techniques have been proposed to address this problem. The goal of the techniques is to obtain reduced test suites that are both cheaper to execute and as effective at detecting faults as the original suite, given that the reduced test suites maintain the same coverage level of the complete test suite required by a test adequacy criterion. These criteria define which parts of the system are going to be tested, how often and under what circumstances. Nevertheless, little attention has been paid to the impact of the criterion choice in test suite reduction research. On the other hand, real-time systems are reactive systems whose behavior is constrained by time. Consequently, time-related faults are specific to these systems. In order to cope with this issue, models for real-time systems must deal with time and, consequently, there are specific test adequacy criteria for them. However, test suite reduction research has not focused on real-time systems, therefore the impact of test adequacy criteria for models of real-time systems on test suite reduction is unknown. In this doctoral research, we aim at investigating the influence of test adequacy criteria on the outcomes of test suite reduction techniques in the context of model-based testing of real-time systems. In particular, we are interested in the Timed Input-Output Symbolic Transition Systems (TIOSTS) model because it is an expressive transition system in which data and time are symbolically defined, and transition systems are the basis for conformance testing of real-time systems. In order to achieve the research objective, first, we defined 19 test adequacy criteria for TIOSTS models. The defined criteria include transition-based criteria, data-flow-oriented criteria and real-time systems criteria. Next, we formalized a hierarchy with these criteria which is partially ordered by the strict inclusion relation. Second, we evaluated the cost-effectiveness of twelve criteria and five test suite reduction techniques in empirical studies of test suite reduction. We evaluated the size, execution time and fault detection of reduced test suites obtained from each combination of criterion and technique. In the experiment, we used TIOSTS specification models of a refilling machine for charging the subway card, a burglar alarm system, and an automated car speed limiter; simulations of the implementations, which generate correct traces for the models; and mutation testing to generate mutants of the specification models, which were also translated to simulations in order to simulate faulty model implementations. Empirical evidence suggests that test adequacy criteria closer to the top of the family obtained reduced test suites with better costeffectiveness regarding fault detection and execution time. With respect to the test suite reduction techniques, the Random technique obtained better cost-effectiveness among the evaluated criteria. Results also suggests that the criteria explain more the variation in fault detection and execution time of reduced test suites than the techniques.