A Metamorphic Testing Approach to NASA GMSEC's Flexible Publish and Subscribe Functionality

Today's software systems are increasingly required to be flexible which is achieved by providing various forms of loose coupling and configuration options. While loose coupling and configuration options facilitate quick adaptation to changing requirements, such flexibility increases the difficulty of system testing. It is often relatively straight-forward to create different configuration options as test cases, but it is typically much more difficult to formulate the expected system behavior, which is known as the oracle problem. NASA's GMSEC software bus is such a flexible system that serves as a central communication channel for software components based on a publish and subscribe architecture where several software components can be dynamically connected to the system. To cope with the difficulties in testing such a flexible software system, we present a metamorphic testing approach that explicitly addresses the test oracle problem. In this paper, we focus on testing the publish and subscribe functionality of GMSEC motivated by the fact that its middleware-based system architecture is the foundation of many of NASA's missions.