| The role of urban railway transportation in urban public traffic system has become more and more important. CBTC system (Communication Based Train Control), for its high efficiency and easy expandability, is gradually considered as the first choice for signal systems used in urban railway transportation system.Vehicle on-board system requires high degree of safety and reliability, so it must be tested before being put into real application. While traditional testing methods cannot meet the requirements of efficiency and sufficiency, software testing technique, on the other hand, is capable of solving this problem. This paper studies the application of white-box testing method in vehicle on-board system from the view point of a developer.After comparing and analyzing general white-box testing methods, branch coverage testing is chosen to be the testing method in this paper. Then improvement on the branch coverage testing is detailed. This improved method makes the testing work easier by dividing the system into a series of independent logic units according to the partition of system function, and by taking branches belonging to the same logic unit as a whole to reduce the number of branches. During testing, each logic unit is tested firstly and then the integrated system is tested. This improved method achieves high efficiency and coverage through step by step testing.Then this paper studies testing process in details, such as: test inputs and outputs selection, test case generation and sorting, test execution and results analysis.Finally, this paper puts the improved branch coverage testing method into practice by using it to test the vehicle on-board system. During testing, the vehicle on-board application is divided into modules, thus the system structure is simplified. Next is selecting the test inputs and outputs according to the inherent features of on-board system. Later test cases are designed for independent module and integrated system. In the execution phase of testing, independent module and integrated system are tested respectively. During integrated system testing, general test platform is constructed to facilitate the testing. After test execution, internal defects in software are located by analyzing test results.Through the actual testing of on-board system, it is verified that the improved branch coverage testing method reduces workload and improves testing efficiency. |
