MC/DC-Like Structural Coverage Criteria for Function Block Diagrams

Programmable Logic Controllers (PLCs) are widely used to implement safety-critical systems and therefore software in PLCs requires thorough testing. Some software in PLCs is written in graphical data flow languages such as Function Block Diagram (FBD). But standard coverage criteria for data flow languages haven't been established. Therefore, we proposed new test coverage criteria for data flow languages in order to confirm the correctness of software in PLCs. As part of this study, we have also developed an automatic test generation technology that generates tests to satisfy the proposed coverage criteria. We evaluated our proposed criteria with actual power plant programs by mutation testing, and confirmed the high ability of our newly developed criteria to detect typical defects.