Thesis for the Degree of Master of Science in Computer Science with specialisation in Software Engineering AUTOMATED TEST CASE GENERATION FOR FUNCTION BLOCK DIAGRAMS USING JAVA PATH FINDER AND SYMBOLIC EXECUTION

Testing Function Block Diagram (FBD) programs for safety-critical software components is of significant importance. Their failure or malfunction may result in a serious outcome and may cause severe damage. Consequently, a certain degree of certification is required to guarantee that the provided test cases cover the logical structure of the safety-critical software components. In practise, testing FBD programs is relatively hard because it is usually performed manually and is prone to human error. Recently, researchers devised an automated test generation tool named CompleteTest that aids control engineers to perform component testing. It analyses safety-critical software components to identify a number of tests needed to achieve maximum coverage required by the industry for operation. CompleteTest is based on a model checker that lacks support for Real and String types which are heavily used in FBD programs. Java Path Finder (JPF) is a model checker that supports different data types and provides an extension supporting symbolic execution named Symbolic Path Finder (SPF). To our knowledge, there has been little research on using symbolic execution in testing FBD programs. Hence, we compare JPF / SPF to CompleteTest and explore possibilities and limitations of symbolic execution on FBD program testing. We show how to translate two FBD programs to Java program representations suitable for model checking using JPF / SPF. In addition, we illustrate how to instrument those Java program representations for automated test case generation using JPF / SPF. The resulting test cases are compared to the test cases generated by CompleteTest evaluating their coverage, efficiency and effectiveness. Even though, the test cases generated by JPF / SPF turn out to be more effective and provide the same coverage as the test cases generated by CompleteTest, more work needs to be done on the efficiency of JPF / SPF optimising its search algorithm. iii