Fevzi Belli

Finite state testing and analysis of graphical user interfaces

Based on finite-state automata (FSA) and equivalent regular expressions, the paper introduces a holistic view of fault modeling that can be carried out as a complementary step to system modeling, revealing much rationalization potential. Appropriate formal notions will be used to introduce efficient algorithms to systematically generate and select test cases. The completeness of the test can be determined exploiting the link coverage of the state transition diagram of the FSA that models both the desired and undesired behavior of the system under test; this enables a precise scalability of the test and analysis process, leading to a better cost-effectiveness The elements of the approach will be narrated by realistic examples which will be used also to validate the approach.

Event‐based modelling, analysis and testing of user interactions: approach and case study

With the growing complexity of computer‐based systems, their graphical user interfaces have also become more complex. Accordingly, the test and analysis process becomes more tedious and costly. This paper introduces a holistic view of fault modelling that is carried out as a complementary step to system modelling, enabling a scalability of the test process, and providing considerable potential for automation. Event‐based notions and tools are used to generate and select test cases systematically. The elements of the approach are illustrated and validated by a case study. This paper does not claim to introduce a novel theoretic approach; rather, it makes use of graph‐theoretic results for a practical and simple, but nevertheless powerful, view of modelling, analysis and testing of graphical user interfaces. Copyright

An approach to the reliability optimization of software with redundancy

An approach to the optimization of software reliability is proposed. The emphasis is put on the software redundancy to achieve fault tolerance, i.e. the results of the optimization process are used to determine the optimal structure of the software to be developed. Two optimization models are formulated covering, respectively, modified recovery block scheme and multiversion programming approaches. Both cases are illustrated by simple examples. The models show that it is possible to formulate and solve some software related reliability optimization problems. They further show that the concept of redundancy to achieve fault tolerance (basic for the traditional theory of reliability) can be used in the field of software reliability optimization. >

Basic Operations for Generating Behavioral Mutants

This paper attempts to subsume the existing great variety of mutation operations to two basic operations, insertion and omission and their combinations. These basic operations are applied to different elements of graph-based models of increasing representation power. A case study applies the approach to these models for generating mutants of different features and compares the fault detection capacity of the mutants generated.

Specification of fault-tolerant system issues by predicate/transition nets and regular expressions-approach and case study

A method to systematically integrate fault tolerance properties into the design of complex software systems is presented. The method exploits a formal specification of the system in which the amount of necessary redundancy can be determined. The system description is based on a combination of a predicate/transition net with regular expressions. The net model provides a formal overview of the system behavior in general, supporting the correct understanding of potential concurrency in the system processes. Regular expressions are used to model the sequential behavior of single-system components in detail. Both model layers provide well-defined levels of error detection; the regular expressions enable the system designer to also determine and introduce redundancy to achieve error correction. The techniques used to describe and analyze system behavior are explained using a case study that contains a stepwise-refined specification and analysis of a multistory shelving system model that has been implemented using the method presented. It is shown that the method applies to any software system which is to be protected against the considered errors. >

Test minimization for human-computer interaction

This paper introduces a model-based approach for minimization of test sets to validate the interaction of human-computer systems. The novelty of the approach is twofold: (i) Test cases generated and selected holistically cover both the behavioral model and the complementary, fault model of the system under test (SUT). (ii) Methods known from state-based conformance testing and graph theory are extended to construct efficient, heuristic search-based algorithms for minimizing the test sets that are constructed in step (i), considering also structural features. Experience shows that the approach can help to considerably save test costs, up to 60%

Test generation and minimization with "basic" statecharts

Model-based testing as a black-box testing technique has grown in importance. The models used represent the relevant features of the system under consideration (SUC), and can also be used as a basis for generating test case sets. In this work we introduce a novel representation of state-charts which subsumes common features of different state-chart variants. Based on this model and well-defined test criteria, efficient algorithms are introduced for generating test case sets. Those test case sets are minimized to cover both the model of SUC and its inversion, i.e., the complementary model.

Towards automation of checklist-based code-reviews

Different types of code-reviews (Fagan-style code-inspections, Parnas-like active design reviews and walkthroughs) have been found to be very useful in improving the quality of software. In many cases reviewers use checklists to guide their analysis during review sessions. However, valuable, checklist-based code-reviews have the principal shortcoming of their high costs due to lack of supporting tools enabling at least partial automation of typical multiple appearing rules. This paper describes an approach towards semi-automation of some steps of individual review processes based on checklists. The method proposed is interactive, i.e. reviewers will be enabled to actualize, extend, and check the consistency and redundancy of their checklists. The basic idea underlying the approach is the usage of a rule-based system, adapting concepts of the compiler theory and knowledge engineering, for acquisition and representation of knowledge about the program. Redundant and conflicting knowledge about the program under study is recognized and solved by means of an embedded truth maintenance system. As a result of fault diagnosis, rules for fault classification are used. Software reliability models are applied to validate the results of each review session. The approach has shown promising preliminary results in analyses of conventional C-programs developed in the automotive industry.

Minimal spanning set for coverage testing of interactive systems

A model-based approach for minimization of test sets for interactive systems is introduced. Test cases are efficiently generated and selected to cover the behavioral model and the complementary fault model of the system under test (SUT). Results known from state-based conformance testing and graph theory are used and extended to construct algorithms for minimizing the test sets, considering also structural features of the SUT.

Model-based mutation testing-Approach and case studies

This paper rigorously introduces the concept of model-based mutation testing (MBMT) and positions it in the landscape of mutation testing. Two elementary mutation operators, insertion and omission, are exemplarily applied to a hierarchy of graph-based models of increasing expressive power including directed graphs, event sequence graphs, finite-state machines and statecharts. Test cases generated based on the mutated models (mutants) are used to determine not only whether each mutant can be killed but also whether there are any faults in the corresponding system under consideration (SUC) developed based on the original model. Novelties of our approach are: (1) evaluation of the fault detection capability (in terms of revealing faults in the SUC) of test sets generated based on the mutated models, and (2) superseding of the great variety of existing mutation operators by iterations and combinations of the two proposed elementary operators. Three case studies were conducted on industrial and commercial real-life systems to demonstrate the feasibility of using the proposed MBMT approach in detecting faults in SUC, and to analyze its characteristic features. Our experimental data suggest that test sets generated based on the mutated models created by insertion operators are more effective in revealing faults in SUC than those generated by omission operators. Worth noting is that test sets following the MBMT approach were able to detect faults in the systems that were tested by manufacturers and independent testing organizations before they were released.