Research And Application Of Interlocking Software Automatic Testing Technology

With the rapid development of Chinese railway, safety is the theme of railwaytransportation and operation forever. In recent years, Computer Interlocking System with itssmall footprint, easy modification, intelligence and other advantages, is widely applied ineach station. Guaranteed in computer hardware, the reliability and safety of the interlockingsoftware have become a focus in the field of railway signal. Testing is one of the methods forensuring the safety and reliability of interlocking software, and the traditional interlockingsoftware testing is difficult to ensure the efficiency and quality of testing, which to someextent relies on the experience and knowledge of testing personnel. Therefore, manyinstitutions begin to study the software automatic testing.The testing data is the basis of the various stages of software testing. It is the emphasisand difficulty in software automatic test that whether can generate and screen the valid testdata. On the basis of studying the functions and hierarchical structure of ComputerInterlocking Software, through the comparative analysis of existing research on generation oftest data, and the application of the test tool named Testbed, combined with software testtheory, a method of test data generation which is based on Petri Nets modeling is proposed.Petri Nets is a kind of directed graph for software test, thus some theories and algorithmsrelated to Graph Theory can be used flexibly. As a result, the advantages of the new methodlie in that the problem is abstracted into directed graph which is more intuitive and clear, andthe test data generation is not affected by the subject factors of tester, the test efficiency andthe test quality are greatly improved.The methods of test data automatic generation from aspects of unit testing and functiontesting are studied.Unit testing is the initial stage of interlocking software dynamic testing activities.Conversion rule from program code to Petri Nets is given out, considering from the internalstructure of the functions or modules. In view that the coverage rate of interlocking softwareunit testing is measured by Statement Coverage, Branch Coverage and Modified ConditionDecision Coverage, path testing is proposed. The various structures of Petri nets and theprocessing of path redundancy situation are fully taken into account in path algorithm.According to the safety requirements of interlocking software, function testing is tocheck out the basic functions and the protection function within safe range of interlockingsystem. The concepts of cut sets and minimal cut sets in the fault tree analysis are introduced.Petri Nets model for safety is established from the point of view that whether the traffic safetyis endangered, through the analysis of the processes of route establishing and route releasing.The basis events set, including various events which endangers the traffic safety, is solved by incidence matrix, and the test cases are generated by dividing the test data input spaceaccording to the safety constraints.Finally, the interlocking software is tested using the foregoing method of generating testcases. The results of test cases execution show that this method can not only satisfy thecoverage requirements, but also can find the software and the design errors, providingreference data for further improvement and optimization of interlocking software.