On the testability of distributed real-time systems

Event-triggered and time-triggered systems are compared with respect to their testability. To facilitate the comparison, three aspects of testability are introduced: test coverage, observability, and controllability. After a brief review of the problems of testing concurrent programs, the author compares the two system architectures with respect to each of these three aspects. The results of the comparisons favor time-triggered systems in all three aspects, most notably with respect to controllability and test coverage. Thus, time-triggered systems are inherently more testable than event-triggered systems. A series of experiments is summarized that shows that it is easy to achieve reproducible testing of time-triggered systems