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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Abstract. Real-time systems are those systems whose behaviors are time dependent. Reliability is one of the characteristics of such systems and testing is one of the techniques that can be used to ensure reliable real-time systems. This paper presents a method for testing real-time systems specified by Timed Input Output Automata (TIOA). Our method is based on the concept of test purposes. The use of test purposes helps reduce the number of test cases generated since an exhaustive testing of a TIOA causes the well-known state explosion problem. The approach we present in this paper consists of three main steps. First, a synchronous product of the specification and test purpose is computed. Then, a subautomaton (called Grid Automata) representing a subset of the state space of this product is derived. Finally, test cases are generated from the resulting grid automata. The test cases generated by our method are executable and can easily be represented in TTCN (Tabular Tree Combined Notation).

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Real-time systems interact with their environment, through time constrained inputloutput events. The misbehavior of real-time systems is generally caused by the violation of the specijied time constraints. Validation of realtime system sojhvare is an important quality control activity in the software lifecycle. Among the validation processes, testing aims at assessing the conformance of an implementation against the reference specijication. One of the important aspects in testing real-time software systems is the fault coverage measurement, which consists of studying the potential faults that can be detected by a test suite generated by a given test generation method. This paper addresses the fault coverage of the Timed Wp-method we have introduced in 191. We present a timed fault model based on the TIOA model for real-time systems specijication. We study the fault coverage of the timed Wp-method with respect to our fault model.

Real-time systems (RTSs) are used in different domains such as telephone switching systems, air traffic control systems and patient monitoring systems. The behavior of RTSs is time-sensitive; that is, RTSs interact with their environment with input and output events under time constraints. The violation of such time constraints is the main cause of the misbehavior of RTSs, and may result in severe damage to human lives and the environment [Mandrioli, D., Morasca, S., & Morzenti, A. 1995. ACM Transactions on Computer Systems, 13(4), 365-398].To prevent failures in RTSs, we must verify that the implementation of an RTS is correct before its deployment. Testing is one of the formal techniques that can be used to achieve this goal. It consists of three main phases: test generation, test execution, and test results analysis. This paper presents a test case generation method for RTSs modeled as Timed Input Output Automata (TIOA). The approach is made in two steps. First, the TIOA describing the system being tested is sampled to construct a subautomaton, which is easily testable (i.e., easy to generate test cases from it). Then, the resulting subautomaton is traversed to generate test cases. Our method is scalable in the sense that it generates a small number of test cases even when the specifications are significant. Moreover, the test cases derived by our method are executable (i.e., they can be run on any error-free implementation of the system being tested).

In this paper, we present a new set of metrics for building secure software systems. The proposed metrics aim to address security risks throughout the entire Software Development Life Cycle (SDLC). The importance of this work comes from the fact that assessing security risks at early stages of the development life cycle can help implement efficient solutions before the software is delivered to the customer. The proposed metrics are defined using the Goal/Question/Metric method. It is anticipated that software engineers will use these metrics in combination with other techniques to detect security risks and prevent these risks from becoming reality. This work is part of a larger research project that aims at examining the concept of "Design for Security". The objective is to investigate software engineering techniques to support security requirements from the very beginning of the development process.