Test generation for high coverage with abstraction refinement and coarsening (ARC)

Testing is the main approach used in the software industry to expose failures. Producing thorough test suites is an expensive and error prone task that can greatly benefit from automation. Two challenging problems in test automation are generating test input and evaluating the adequacy of test suites: the first amounts to producing a set of test cases that accurately represent the software behavior, the second requires defining appropriate metrics to evaluate the thoroughness of the testing activities. Structural testing addresses these problems by measuring the amount of code elements that are executed by a test suite. The code elements that are not covered by any execution are natural candidates for generating further test cases, and the measured coverage rate can be used to estimate the thoroughness of the test suite. Several empirical studies show that test suites achieving high coverage rates exhibit a high failure detection ability. However, producing highly covering test suites automatically is hard as certain code elements are executed only under complex conditions while other might be not reachable at all. In this thesis we propose Abstraction Refinement and Coarsening (ARC), a goal oriented technique that combines static and dynamic software analysis to automatically generate test suites with high code coverage. At the core of our approach there is an abstract program model that enables the synergistic application of the different analysis components. In ARC we integrate Dynamic Symbolic Execution (DSE) and abstraction refinement to precisely direct test generation towards the coverage goals and detect infeasible elements. ARC includes a novel coarsening algorithm for improved scalability. We implemented ARC-B, a prototype tool that analyses C programs and produces test suites that achieve high branch coverage. Our experiments show that the approach effectively exploits the synergy between symbolic testing and reachability analysis outperforming state of the art test generation approaches. We evaluated ARC-B on industry relevant software, and exposed previously unknown failures in a safety-critical software component

THE MATURATION OF WESTERN EQUINE ENCEPHALOMYELITIS VIRUS AND ITS RELEASE FROM CHICK EMBRYO CELLS IN SUSPENSION

Experiments are presented in which the plaque assay technique was used to study the intracellular appearance and release of Western equine encephalomyelitis virus in suspensions of infected chick embryo fibroblasts. No intracellular virus could be found during the 1st hour after adsorption in spite of the fact that more than 1014 cells per ml. proved to be infected. This is taken to indicate that the infecting particle loses its infectivity upon entering a susceptible cell. The first progeny virus was detectable in the cells between 1 and 2 hours after infection, and it increased in amount exponentially during the following 3 hours. The released virus as measured in the supernatant fluid increased at the same rate as the intracellular virus but exceeded it in amount by a factor of about twenty at all times during the period of exponential increase. More than 100 particles were spontaneously released from each cell, by the end of the period of exponential increase, yet the maximum number of intracellular infective particles at any instant during this period was never more than an average of from 4 to 10 per cell. Calculations based on these findings indicate that, on the average, a virus particle is released from the cell within 1 minute after it gains the property of infectiousness

Exact Gap Computation for Code Coverage Metrics in ISO-C

Test generation and test data selection are difficult tasks for model based testing. Tests for a program can be meld to a test suite. A lot of research is done to quantify the quality and improve a test suite. Code coverage metrics estimate the quality of a test suite. This quality is fine, if the code coverage value is high or 100%. Unfortunately it might be impossible to achieve 100% code coverage because of dead code for example. There is a gap between the feasible and theoretical maximal possible code coverage value. Our review of the research indicates, none of current research is concerned with exact gap computation. This paper presents a framework to compute such gaps exactly in an ISO-C compatible semantic and similar languages. We describe an efficient approximation of the gap in all the other cases. Thus, a tester can decide if more tests might be able or necessary to achieve better coverage.Comment: In Proceedings MBT 2012, arXiv:1202.582

Domestic chickens activate a piRNA defense against avian leukosis virus

PIWI-interacting RNAs (piRNAs) protect the germ line by targeting transposable elements (TEs) through the base-pair complementarity. We do not know how piRNAs co-evolve with TEs in chickens. Here we reported that all active TEs in the chicken germ line are targeted by piRNAs, and as TEs lose their activity, the corresponding piRNAs erode away. We observed de novo piRNA birth as host responds to a recent retroviral invasion. Avian leukosis virus (ALV) has endogenized prior to chicken domestication, remains infectious, and threatens poultry industry. Domestic fowl produce piRNAs targeting ALV from one ALV provirus that was known to render its host ALV resistant. This proviral locus does not produce piRNAs in undomesticated wild chickens. Our findings uncover rapid piRNA evolution reflecting contemporary TE activity, identify a new piRNA acquisition modality by activating a pre-existing genomic locus, and extend piRNA defense roles to include the period when endogenous retroviruses are still infectious. DOI: http://dx.doi.org/10.7554/eLife.24695.00

The discovery of endogenous retroviruses

When endogenous retroviruses (ERV) were discovered in the late 1960s, the Mendelian inheritance of retroviral genomes by their hosts was an entirely new concept. Indeed Howard M Temin's DNA provirus hypothesis enunciated in 1964 was not generally accepted, and reverse transcriptase was yet to be discovered. Nonetheless, the evidence that we accrued in the pre-molecular era has stood the test of time, and our hypothesis on ERV, which one reviewer described as 'impossible', proved to be correct. Here I recount some of the key observations in birds and mammals that led to the discovery of ERV, and comment on their evolution, cross-species dispersion, and what remains to be elucidated

Alien Registration- Baluda, Ben (Lincoln, Penobscot County)

https://digitalmaine.com/alien_docs/7471/thumbnail.jp