(A) testing method for task interactions of embedded software using message sequence charts

Abstract

Modern embedded software is often quite complex for testing interactions among tasks, and it is desirable to automate testing process as much as possible for cost effective testing. In this dissertation, we demonstrate how to automatically generate test cases from a set of scenarios by constructing a semantically equivalent global behavior model. We separately describe internal interactions of each external input event using Message Sequence Charts (MSCs). Since brute-force approach to translate MSCs into a finite state machine (FSM) results in a large number of states and transitions, we propose a state-reduced FSM, global FSM (GFSM), by encoding the possible configurations of system into states. When scenarios are to be executed concurrently, as is often the case for embedded software, the number of transitions grows too quickly for the approach to remain practical. In this dissertation, we demonstrate that partial order reduction technique is useful in reducing the number of transitions. We illustrate how to identify a sequence of message exchanges, independent region, that are semantically equivalent. When concurrent messages are interleaved, the number of transitions can be reduced by excluding the messages within the independent region. Finally, test cases are generated from the GFSM to satisfy either the state- or transition-tour coverage criteria, and represented in terms of the required external events` sequences and internal interactions. We develop a software toolset, a graphical MSCs editor and test case generator, to automatically generate test cases. We have successfully applied the proposed approach to specify a major portion of software requirements running on a digital TV.