Nina Yevtushenko

Extended Finite State Machine based test derivation strategies for telecommunication protocols

In this paper, we consider the problem of test derivation based on an Extended Finite State Machine EFSM) that is widely used for describing the behavior of telecommunication protocols and software. An EFSM augments a classical Finite State Machine (FSM) with context variables, input/output parameters and predicates. Tests based on various coverage criteria for EFSMs do not capture many functional faults and thus, there is a strong need for tests checking functional properties. Moreover, since there are no constructive necessary and sufficient conditions for checking whether two arbitrary EFSMs are equivalent, most methods are based on some kind of a transition tour, despite of the fact that such methods do not provide test suites with the guaranteed fault coverage. Given possibly nondeterministic and partial EFSM, we consider a transition tour of an FSM obtained by the simulation of the initial EFSM and provide some experimental results that such a test suite detects a number of inconsistencies in available protocol implementations with respect to protocol specifications. Since a transition tour augmented with state identifiers is known to have the higher fault coverage, we also discuss how state identifiers can be generated without facing the state explosion problem. Correspondingly, we consider FSM slices that are obtained by deleting from the initial EFSM all the context variables and possibly, input and output parameters. As the obtained FSM can be nondeterministic, a state identifier should contain separating sequences for pairs of states and we adapt the known techniques for deriving separating sequences for nonobservable partial FSMs

Towards Model based Testing for Software Defined Networks.

Software Defined Networks (SDNs) and corresponding platforms are expected to be widely used in future generation networks and especially deployed and activated on-demand as agile networking control service components. The correct functioning of SDN platforms must be assured, i.e., such platforms should be thoroughly tested before deployment. After thorough verification of SDN controllers and switches, the composition of them still requires additional testing in order to guarantee the absence of critical faults. We propose a model based testing technique for checking SDN platforms that relies on appropriate graph enumeration. In particular, we define a fault model where the fault domain contains the wrongly and correctly implemented paths allowed with respect to the underlying resource connectivity graph. We also establish the conditions for deriving a complete test suite with respect to such fault model under black box and white box testing

Scalable QoE Prediction for Service Composition

In this paper, we present an approach for scalable QoE estimation/prediction of a composition of given services. The approach relies on using logic circuits/networks for the QoE prediction. Given two logic circuits that predict the QoE values of two service components, we propose a method for synthesizing the resulting logic circuit that predicts the QoE of the overall service composition. As the complexity of this resulting circuit significantly depends on the complexity of an implementation of a MIN function, we present an experimental evaluation of the complexity of the corresponding circuit.

Test Derivation for SDN-Enabled Switches: A Logic Circuit Based Approach

The paper is devoted to testing critical Software Defined Networking (SDN) components and in particular, SDN-enabled switches. A switch can be seen as a forwarding device with a set of configured rules and thus, can be modelled and analyzed as a ‘stateless’ system. Correspondingly, in this paper we propose to use appropriate logic circuits or networks to model the switch behavior. Both active and passive testing modes can benefit from such representation. First, this allows applying well-known test generation strategies such as for example, test derivation techniques targeting Single Stuck-at Faults (SSFs). We also specify a number of mutation operators for switch rules and propose an algorithm for eliminating equivalent mutants via SAT solving. Logic circuits simulating the behavior of the switches can be effectively utilized for run-time verification, and such logic circuit based approach is also discussed in the paper. Preliminary experimental results with Open vSwitch, on one hand, demonstrate the necessity of considering new fault models for logic circuits (apart from, for example well established SSFs) and on the other hand, confirm the efficiency of the proposed test generation and verification techniques.

Source code optimization using equivalent mutants

Abstract Context: A mutant is a program obtained by syntactically modifying a program’s source code; an equivalent mutant is a mutant, which is functionally equivalent to the original program. Mutants are primarily used in mutation testing, and when deriving a test suite, obtaining an equivalent mutant is considered to be highly negative, although these equivalent mutants could be used for other purposes. Objective: We present an approach that considers equivalent mutants valuable, and utilizes them for source code optimization. Source code optimization enhances a program’s source code preserving its behavior. Method: We showcase a procedure to achieve source code optimization based on equivalent mutants and discuss proper mutation operators. Results: Experimental evaluation with Java and C programs demonstrates the applicability of the proposed approach. Conclusion: An algorithmic approach for source code optimization using equivalent mutants is proposed. It is showcased that whenever applicable, the approach can outperform traditional compiler optimizations.

Proactive Trust Assessment of Systems as Services.

The paper is devoted to the trust assessment problem for specific types of software/hardware systems,nnamely Systems as Services. We assume that such systems are designed and utilized in all applicationndomains, and therefore the aspects of trust are becoming crucial. Moreover, these systems are mainly usednon-demand and are often represented by a composition of ‘smaller’ services. Thus, an effective method fornestimating/assessing the trust level of a given component service (or a system as a whole) needs to benutilized. Most known methods and techniques for trust evaluation mainly rely on the passive testing andnsystem monitoring; in this paper, we propose a novel approach for this problem taking advantage of activentesting techniques. Test sequences to be applied to a system/service under test are derived based onndetermining the critical values of non-functional service parameters. A set of these parameters can benobtained via a static code analysis of the system/service or by addressing available experts. Machinenlearning techniques can be applied later on, for determining critical parameter values and thus, derivingncorresponding test sequences. The paper contains an illustrative example of RESTFul web service whichncomponents are checked w.r.t. critical trust properties.