The selection of appropriate test cases is an important issue for conformance testing of protocol implementations as well as in software engineering. A number of methods are known for the selection of a test suite based on the specification of the implementation under test, assumed to be given in the form of a finite state machine. This paper presents a new method which provides a logical link between several of the known methods. Called "partial W method", it has general applicability, full fault detection power, and yields shorter test suites than the W method. The second part of the paper discusses various other issues which have an impact on the selection of a suitable test suite. This includes the consideration of interaction parameters, various test architectures for protocol testing, and the fact that many specifications do not satisfy the assumptions made by most test selection methods, such as complete definition, a correctly implemented reset function, a limited number of states in the implementation, and determinism.

Real-time systems interact with their environment using time constrained input/output signals. Examples of real-time systems include patient monitoring systems, air traffic control systems, and telecommunication systems. For such systems, a functional misbehavior or a deviation from the specified time constraints may have catastrophic consequences [27]. Therefore, ensuring the correctness of real-time systems becomes necessary. Two different techniques are usually used to cope with the correctness of a software system prior to its deployment, namely, verification and testing. In this paper, we address the issue of testing real-time software systems specified as a Timed Input Output Automaton (TIOA). TIOA is a variant of timed automaton [1], [2], [22], [29]. We introduce the syntax and semantics of TIOA. We present the potential faults that can be encountered in a timed system implementation. We study these different faults based on TIOA model and look at their effects on the execution of the system using the region graph. We present a method for generating timed test cases. This method is based on a state characterization technique and consists of the following three steps: First, we sample the region graph using a suitable granularity, in order to construct a subautomaton easily testable, called Grid Automaton. Then, we transform the Grid Automaton into a Nondeterministic Timed Finite State Machine (NTFSM). Finally, we adapt the Generalized Wp-method [23] to generate timed test cases from NTFSM. We assess the fault coverage of our test cases generation method and prove its ability to detect all the possible faults. Throughout the paper, we use examples to illustrate the various concepts and techniques used in our approach.

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