Modelling and design of the formal approach for generating test sequences of ETCS level 2 based on the CPN

ETCS Level 2 (European Train Control System Level 2, ETCS-2) has drawn particularly attention from researchers and industries. A new CPN model-based formal approach for test cases and sequences generation is proposed in this paper to increase the test automation degree of the ETCS-2 system and subsystems. In this paper, a set of modelling rules is presented firstly to make the Coloured Petri Net (CPN) model more suitable for test generation. Then, an automated test approach is described in detail, which includes an automatic test case generating algorithm and a type of automatic test sequence searching algorithm. The generated set of test cases satisfies specified coverage. The test sequence searching algorithm guarantees the results satisfying the minimum number of test sequences covering all test cases. The output of this approach is a set of well-formed XML (Extensible Markup Language) file to increase the automation degree of the test executing process. Finally, a partial model of ETCS-2 On-Board subsystem is built and analysed using the CPN Tools as a case study. The model-based formal approach is implemented on this model and the test cases and test sequences are all generated in a form of XML. The conclusion show that the CPN-model based testing approach can be used to improve the automation of the testing procedure and the generated test cases can meet the relative requirement.