As software systems increasingly are used to control critical infrastructure, transportation systems and factory equipment, the use of proper testing methods has become more important. Systems that can cause harm to people, equipment or the environment they operate in are called safety critical systems.The suppliers of safety critical systems makes use of safety analysis methods to investigate possible hazards. The ouput from the analysis are possible causes and effects of the hazards found. These results are a large part of the basis for writing safety requirements for the system.The safety requirements should be tested thoroughly to avoid accidents. It is important that the right testing technique is applied to test these systems. The consequences of a system failure can be very high, so it is crucial to make use of a testing technique that has an approach that fits safety testing best. This thesis presents an experiment that looks into these questions. Also, the experiment investigates how the barrier model and safety analysis results helps in writing test cases for these systems.