Interaction Coverage Meets Path Coverage by SMT Constraint Solving

Abstract. We present a novel approach for generating interaction combinations based on SMT constraint resolution. Our approach can generate maximal inter-action coverage in the presence of general constraints as supported by the un-derlying solver. It supports seeding with general predicates, which allows us to combine it with path exploration such that both interaction and path coverage goals can be met. Our approach is motivated by the application to behavioral model-based testing in the Spec Explorer tool, where parameter combinations must be generated such that all path conditions of a model action have at least one combination which enables the path. It is applied in a large-scale project for model-based quality assurance of interoperability documentation at Microsoft.

Timed Implementation Relations for the Distributed Test Architecture

In order to test systems that have physically distributed interfaces, called ports, we might use a distributed approach in which there is a separate tester at each port. If the testers do not synchronise during testing then we cannot always determine the relative order of events observed at different ports and this leads to new notions of correctness that have been described using corresponding implementation relations. We study the situation in which each tester has a local clock and timestamps its observations. If we know nothing about how the local clocks relate then this does not affect the implementation relation while if the local clocks agree exactly then we can reconstruct the sequence of observations made. In practice, however, we are likely to be between these extremes: the local clocks will not agree exactly but we have some information regarding how they can differ. We start by assuming that a local tester interacts synchronously with the corresponding port of the system under test and then extend this to the case where communications can be asynchronous, considering both the first-in-first-out (FIFO) case and the non-FIFO case. The new implementation relations are stronger than implementation relations for distributed testing that do not use timestamps but still reflect the distributed nature of observations. This paper explores these alternatives and derives corresponding implementation relations

Overcoming controllability problems in distributed testing from an input output transition system

This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 Springer VerlagThis paper concerns the testing of a system with physically distributed interfaces, called ports, at which it interacts with its environment. We place a tester at each port and the tester at port p observes events at p only. This can lead to controllability problems, where the observations made by the tester at a port p are not sufficient for it to be able to know when to send an input. It is known that there are test objectives, such as executing a particular transition, that cannot be achieved if we restrict attention to test cases that have no controllability problems. This has led to interest in schemes where the testers at the individual ports send coordination messages to one another through an external communications network in order to overcome controllability problems. However, such approaches have largely been studied in the context of testing from a deterministic finite state machine. This paper investigates the use of coordination messages to overcome controllability problems when testing from an input output transition system and gives an algorithm for introducing sufficient messages. It also proves that the problem of minimising the number of coordination messages used is NP-hard

Model-Based Filtering of Combinatorial Test Suites

International audienceTobias is a combinatorial test generation tool which can efficiently generate a large number of test cases by unfolding a test pattern and computing all combinations of parameters. In this paper, we first propose a model-based testing approach where Tobias test cases are first run on an executable UML/OCL specification. This animation of test cases on a model allows to filter out invalid test sequences produced by blind enumeration, typically the ones which violate the pre-conditions of operations, and to provide an oracle for the valid ones. We then introduce recent extensions of the Tobias tool which support an incremental unfolding and filtering process, and its associated toolset. This allows to address explosive test patterns featuring a large number of invalid test cases, and only a small number of valid ones. For instance, these new constructs could mandate test cases to satisfy a given predicate at some point or to follow a given behavior. The early detection of invalid test cases improves the calculation time of the whole generation and execution process, and helps fighting combinatorial explosion

Deciding to enter tertiary education and taking on debt : a longitudinal perspective

This thesis describes a program of research designed to investigate longitudinally the role of debt in a cohort of 1232 final-year New Zealand secondary school students, their tertiary entry decisions and their attitudes towards tertiary education and student debt. It follows some of these students into their first year out of school into tertiary education or otherwise. Two surveys were conducted that employed the Attitude to Debt Scale (Davies and Lea, 1995) to address students’ debt and savings behaviour and estimates, tertiary education entry decisions, and attitudes to tertiary education and term-time working. Debt attitudes are found to be more complex than previously proposed, and this has significant ramifications for debt attitude theory and research. Longitudinal comparisons suggest students’ views regarding debt necessity does not change but their attitude to avoiding does. Students become more or less avoidant of debt depending on their circumstances. However, debt attitude results still support many of the findings of earlier research such as debt acquisition preceding a more tolerant attitude change. Debt and tertiary education attitudes are not well predicted. Students report engaging in term-time working to limit their student loans, but engaging in term-time working results in lower grades in their studies. Those from the middle and higher socio-economic classes are more likely to be positive towards tertiary education, and thus entrants, compared with the lower socio-economic classes. However, the results do not suggest this is due to debt attitudes or fear of debt

Distinguishing sequences for partially specified FSMs

Distinguishing Sequences (DSs) are used inmany Finite State Machine (FSM) based test techniques. Although Partially Specified FSMs (PSFSMs) generalise FSMs, the computational complexity of constructing Adaptive and Preset DSs (ADSs/PDSs) for PSFSMs has not been addressed. This paper shows that it is possible to check the existence of an ADS in polynomial time but the corresponding problem for PDSs is PSPACE-complete. We also report on the results of experiments with benchmarks and over 8 * 106 PSFSMs. © 2014 Springer International Publishing

Using schedulers to test probabilistic distributed systems

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s00165-012-0244-5. Copyright © 2012, British Computer Society.Formal methods are one of the most important approaches to increasing the confidence in the correctness of software systems. A formal specification can be used as an oracle in testing since one can determine whether an observed behaviour is allowed by the specification. This is an important feature of formal testing: behaviours of the system observed in testing are compared with the specification and ideally this comparison is automated. In this paper we study a formal testing framework to deal with systems that interact with their environment at physically distributed interfaces, called ports, and where choices between different possibilities are probabilistically quantified. Building on previous work, we introduce two families of schedulers to resolve nondeterministic choices among different actions of the system. The first type of schedulers, which we call global schedulers, resolves nondeterministic choices by representing the environment as a single global scheduler. The second type, which we call localised schedulers, models the environment as a set of schedulers with there being one scheduler for each port. We formally define the application of schedulers to systems and provide and study different implementation relations in this setting

Using genetic algorithms to generate test sequences for complex timed systems

The generation of test data for state based specifications is a computationally expensive process. This problem is magnified if we consider that time con- straints have to be taken into account to govern the transitions of the studied system. The main goal of this paper is to introduce a complete methodology, sup- ported by tools, that addresses this issue by represent- ing the test data generation problem as an optimisa- tion problem. We use heuristics to generate test cases. In order to assess the suitability of our approach we consider two different case studies: a communication protocol and the scientific application BIPS3D. We give details concerning how the test case generation problem can be presented as a search problem and automated. Genetic algorithms (GAs) and random search are used to generate test data and evaluate the approach. GAs outperform random search and seem to scale well as the problem size increases. It is worth to mention that we use a very simple fitness function that can be eas- ily adapted to be used with other evolutionary search techniques

Tbx2 and Tbx3 induce atrioventricular myocardial development and endocardial cushion formation

A key step in heart development is the coordinated development of the atrioventricular canal (AVC), the constriction between the atria and ventricles that electrically and physically separates the chambers, and the development of the atrioventricular valves that ensure unidirectional blood flow. Using knock-out and inducible overexpression mouse models, we provide evidence that the developmentally important T-box factors Tbx2 and Tbx3, in a functionally redundant manner, maintain the AVC myocardium phenotype during the process of chamber differentiation. Expression profiling and ChIP-sequencing analysis of Tbx3 revealed that it directly interacts with and represses chamber myocardial genes, and induces the atrioventricular pacemaker-like phenotype by activating relevant genes. Moreover, mutant mice lacking 3 or 4 functional alleles of Tbx2 and Tbx3 failed to form atrioventricular cushions, precursors of the valves and septa. Tbx2 and Tbx3 trigger development of the cushions through a regulatory feed-forward loop with Bmp2, thus providing a mechanism for the co-localization and coordination of these important processes in heart development