Testing Safety Plcs Using Quickcheck

The testing of safety-related industrial systems is usually carried out by means of checklists. A tester has a list of scenarios that he or she manually applies to the system to check whether the system behaves according to its specification. However, operators behave unpredictably. Their behavior may not be covered by the set of scenarios tested and may lead to dangerous situations. To avoid this, randomized test case generation can be useful as it allows for unanticipated scenarios. The presented framework uses a tool for randomized test case generation, QuickCheck, to trigger event sequences that are then applied to a Safety Programmable Logic Controller (Safety PLC). Experiments show that this concept is capable of finding errors in safety code or increasing the tester's confidence in the correctness of the code by exhibiting a large number of passing test cases. While this concept proves to be powerful, it does not require much effort from the tester as the execution of test cases is done without user interaction.