Testing concurrency and communication in distributed objects

Concurrency and communication are two of the key features of distributed systems. These features can make systematic testing of distributed systems a complex task. A major problem is the explosion of the test space because of the potential for arbitrary interference of concurrent threads. This paper describes an approach for systematic testing of such systems in an object-oriented context. We use statecharts for system specification, and model the system behaviour as event-sequences. A test case, therefore, is primarily an event-sequence with concurrent threads represented as interleaving events. Communication-states with associated events represent communication between objects. The test-space explosion is controlled by an extension to Chow's (1978) algorithm for generating test sequences for finite state machines. The number of test sequences we require is O(n/sup 2/), where n is the sum of all events in all concurrent statecharts.