| With the rapid development of urban mass transition in recent years, CBTC (Communication Based Train Control) system, characterized by its safety and effectiveness, has become the first choice of the signal system. Home-made CBTC, having acquired independent intellectual property rights, has come into trial run of engineering projects and will break the monopoly of foreign producers. Vehicle onboard controller, the core of CBTC system, is responsible for all the safe-driving related control commends and must go through thoroughly strict testing and verification before coming into use.Well organized and standardized test cases will lead to efficient test implementation. So this paper is focused on the method of design and optimization of test cases for VOBC equipment. It is first introduced that VOBC test platform has applied the hybrid test method. Requirements-Based testing is of great importance in safety critical system. Because of complex function and large number of interfaces of onboard system, Cause-effect graphs are chosen to design test cases.Then we abstract function features from VOBC subsystem requirement specification and construct the test requirements traceability matrix in order to make sure that all the requirements are satisfied. Then we describe each of the requirements in the pattern of cause-effect graph. By use of the tool for generating test cases, Bender-RBT, complete test cases are created and reviewed. Strong coverage can be also achieved if the graph is proper.The iteration and evolution in the process of VOBC equipment development often results in redundant cases, and thus we can reduce the test cases to improve the test efficiency. This paper reviewed current test cases reduction methods and proposed a new testing requirement reduction model that can describe the interrelations among the testing requirements in detail. The results show that this method is helpful to generate smaller test suite and contribute to effective testing. |
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