Research On Test Case And Test Sequence Generation Method For CTCS-2 On-board Equipment

The on-board equipment of CTCS-2(C2OBE)is required to be safety-critical,which must undergo a series of strict testing phases before being put into use.The simulation test is an important phase among the testing phases,which performs functional testing on C2 OBE.The test cases of C2 OBE are fundamental to simulation test,and thus determine the quality of test work.However,the current generation methods of test cases for C2 OBE mainly focus on the normal scenarios,which fail to cover the abnormal scenarios sufficiently.Furthermore,in the simulation test of C2 OBE,all the test cases need to be connected into test sequences.However,when there are new test cases being added to the test case library,the existing methods need to generate the test sequence from scratch to cover both new test cases and existing test cases.This disables the efforts on existing test sequences and scripts,and brings a large amount of additional cost in preparing test scripts.This thesis addresses the above issues in terms of test case generation and test sequence generation,and the major contributions are as follows.1.In order to cover the abnormal scenarios of C2 OBE in a more sufficient way,a test case generation method is proposed based on Scenario Method and HAZOP.Firstly,under the Scenario Method framework,the normal scenarios are modeled as basic flows according to the normal functional logic and process.Secondly,considering each basic flow as a node parameter,HAZOP is applied to derive the alternate flows in abnormal scenarios.And a scenario graph is created based on both the basic flows and the alternate flows.Thirdly,all-path search algorithm is proposed to find out all possible paths from the graph.And consider them as testing scenarios for test case generation.Finally,take the level conversion function of C2 OBE as case study to generate test cases and compare them with the existing test case library.The result shows that the test cases generated by this method can cover more abnormal scenarios,which improves the effectiveness of testing C2 OBE.2.In order to generate test sequence to cover the new test cases with the minimum test cost while reuse the existing test sequences and scripts,this thesis converts this aim into the directed rural postman problem in graph theory,and thus proposes a test sequences optimization generation method based on the coverage set concept.Firstly,a directed graph model with the coverage set is defined,and a decision criterion for its connectivity is proposed.Then,if the test cases in the coverage set can constitute a weakly connected graph,a test sequence generation algorithm is designed based on the capacity network,which can obtain the optimal test sequence in polynomial time.Otherwise,if the test cases in the coverage set cannot constitute a weakly connected graph,a test sequence generation algorithm is designed based on the genetic algorithm,which can efficiently obtain the approximately optimal test sequence.Finally,the effectiveness of the method is verified by generating test sequences for the test cases of C2 OBE.3.In order to improve the testing efficiency and ensure the correctness of the test data,this thesis designs and implements an assistive tool for C2 OBE.This tool integrates the proposed optimization generation method,and generates the test sequence automatically.In addition,the tool can help testers to compile the balise information and track circuit information in the test sequence with the form of visual graphics.It can also automatically export test scripts for test execution.Thus,it provides tool support for simulation test of C2 OBE.