Research On Safety-oriented Combinatorial Testing For CTCS-2 Onboard Equipment

As a core component of Chinese Train Control System-Level 2(CTCS-2),the onboard equipment ensures both safety and efficiency of train operation.The safety of onboard equipment needs to be highly assured.Performing safety-oriented testing on CTCS-2 onboard equipment software contributes to enhancing its safety.However,currently,it fails to conduct effective safety-oriented testing on CTCS-2 onboard equipment,as there are many interactions of factors are ignored,especially the interactions of runtime exceptions and bias.These interactions typically exist in both external inputs and internal states/configurations,e.g.,balise messages and track circuit information.In real-world testing,such interactions are often handled in a manual way that fails to achieve sufficient coverage.As a result,it causes to decrease the effectiveness of the safety-oriented testing.Combinatorial testing is a software testing technique that performs efficient testing for the system,while preserving fault detection ability and combinatorial coverage on the interactions.Based on combinatorial testing technique,this thesis addresses the problem by proposing a safety-oriented combinatorial testing method for CTCS-2 onboard equipment.This method considers both potential runtime exceptions and bias of CTCS-2 onboard equipment,and thus generates safety-oriented combinatorial tests to cover the interactions of factors.The major contributions of this thesis are:1.Safety analysis is performed on the CTCS-2 onboard equipment for testing purpose.Specifically,first,a Petri net model is created for onboard equipment to describe its function.Based on the model,the key events are identified,which would affect the functional safety.And the unexpected scenarios are also analyzed from the perspective of the testability.Second,Fault Tree Analysis method is applied to the events and unexcepted scenarios to find out the potential faulty factors and input deviations.2.A combinatorial test generation approach is proposed to generate safety-oriented combinatorial tests for onboard equipment.Specifically,first,a hierarchical input model for test generation is created based on the identified factors and equipment structure.Second,a hierarchical combinatorial test generation algorithm with two-phase strategy is proposed,which generates safety-oriented tests efficiently for the onboard equipment.3.Taking the level transition scenario as case study,the application steps of the proposed method are illustrated.And the resulted combinatorial tests are further implemented as the standard executable tests.Through test execution,the feasibility and validity of the method are verified,in terms of preserving safety,executability and efficiency.