Efficient FBD Test Generation Through Program Slicing

Abstract: Program slicing has been used as a way to improve the efficiency of debugging and program analysis. Nowadays, automated test generation is being used to create tests automatically by analysing the program structure and suggesting necessary tests. This kind of techniques are prone to efficiency problems when applied to large programs containing many lines of code. This is especially true for software in industrial practice, such as the ones running on Programmable logic controllers (PLC) that are used in a wide variety of tasks from toys to avionics and rail transport. Function Block Diagram (FBD) is a language used for programming PLCs that has gained lots of attention in industrial practice due to its graphical nature. These FBD programs are often used in real time and safety critical systems, and these systems require extensive testing in order to prove that they pass safety requirements of their respective domains. In order to improve the efficiency of applying automated test generation on FBD programs we propose two FBD program slicing algorithms based on the structure of these diagrams and how they are programmed. These FBD program slicing algorithms are applied on several industrial programs for PLCs in order to evaluate their feasibility and what effect slicing has on test generation. Six FBD programs were selected out of 189 provided by Bombardier Transportation Sweden AB. The six programs were sliced according to these FBD slicing algorithms and then evaluated in terms of efficiency and applicability. Our results suggest that slicing can be used to reduce the needed generation time and memory usage required for automated test generation. However, our observations show that slicing can also increase the number of test cases generated and how this test cases are merged into one test suite for the entire program.