Abstract--Real-time embedded systems (RTESs) are becoming increasingly ubiquitous, controlling a wide variety of popular and safety-critical devices. Effective testing techniques could improve the dependability of these systems. In this paper we present an approach for testing RTESs, intended specifically to help RTES application developers detect faults related to functional correctness. Our approach consists of two techniques that focus on exercising the interactions between system layers and between the multiple user tasks that enact application behaviors. We present results of an empirical study that shows that our techniques are effective at detecting faults.