CODE DEFENDERS: A Mutation Testing Game

Mutation testing is endorsed by software testing researchers for its unique capability of providing pragmatic estimates of a test suite's fault detection capability, and for guiding testers in improving their test suites. In practice, however, wide-spread adoption of mutation testing is hampered because any non-trivial program results in huge numbers of mutants, many of which are either trivial or equivalent, and thus useless. Trivial mutants reduce the motivation of developers in trusting and using the technique, while equivalent mutants are frustratingly difficult to handle. These problems are exacerbated by insufficient education on testing, which often means that mutation testing is not well understood in practice. These are examples of the types of problems that gamification aims to overcome by making such tedious activities competitive and entertaining. In this paper, we introduce the first steps towards building Code Defenders, a mutation testing game where players take the role of an attacker, who aims to create the most subtle non-equivalent mutants, or a defender, who aims to create strong tests to kill these mutants. The benefits of such an approach are manifold: The game can serve an educational role by engaging learners in mutation testing activities in a fun way. Experienced players will produce strong test suites, capable of detecting even the most subtle bugs that other players can conceive. Equivalent mutants are handled by making them a special part of the gameplay, where points are at stake in duels between attackers and defenders

Mitigating energy system vulnerability by implementing a microgrid with a distributed management algorithm

This work presents a management strategy for microgrid (MG) operation. Photovoltaic (PV) and wind generators, as well as storage systems and conventional units, are distributed over a wide geographical area, forming a distributed energy system, which is coordinated to face any contingency of the utility company by means of its isolated operation. The management strategy divides the system into three main layers: renewable generation, storage devices, and conventional units. Interactions between devices of the same layer are determined by solving an economic dispatch problem (EDP) in a distributed manner using a consensus algorithm (CA), and interactions between layers are determined by means of a load following strategy. In this way, the complex behaviour of PV and wind generation, the battery storage system, and conventional units has been effectively combined with CA to solve EDP in a distributed manner. MG performance and its vulnerability are deeply analysed by means of an illustrative case study. From the observed results, vulnerability under extreme conditions could be reduced up to approximately 30% by coupling distributed renewable generation and storage capacity with an energy system based on conventional generation

A detailed investigation of the effectiveness of whole test suite generation

© 2016 The Author(s)A common application of search-based software testing is to generate test cases for all goals defined by a coverage criterion (e.g., lines, branches, mutants). Rather than generating one test case at a time for each of these goals individually, whole test suite generation optimizes entire test suites towards satisfying all goals at the same time. There is evidence that the overall coverage achieved with this approach is superior to that of targeting individual coverage goals. Nevertheless, there remains some uncertainty on (a) whether the results generalize beyond branch coverage, (b) whether the whole test suite approach might be inferior to a more focused search for some particular coverage goals, and (c) whether generating whole test suites could be optimized by only targeting coverage goals not already covered. In this paper, we perform an in-depth analysis to study these questions. An empirical study on 100 Java classes using three different coverage criteria reveals that indeed there are some testing goals that are only covered by the traditional approach, although their number is only very small in comparison with those which are exclusively covered by the whole test suite approach. We find that keeping an archive of already covered goals along with the tests covering them and focusing the search on uncovered goals overcomes this small drawback on larger classes, leading to an improved overall effectiveness of whole test suite generation

PRECONCENTRATION OF COPPER FROM DIFFERENT SAMPLES BY DISPERSIVE LIQUID-LIQUID MICROEXTRACTION

Sample preparation is a critical step of any analytical protocol. Nowadays the goals to be reached are the best results, in the shortest time, with minimal contamination, low reagent consumption and generation of minimal waste. Dispersive liquid-liquid microextraction is a miniaturized sample preparation procedure inside Green Chemistry because the low volume of dissolvent employed. All parameters that influence on the preconcentration of copper have been optimized. The detection limit was 7.9 μg L-1. The proposed method was successfully applied to the preconcentration and determination of copper in food, vegetation, and water samples and in two standard reference materials

The influence of pre-fermentative maceration and ageing factors on ester profile and marker determination of Pedro Ximenez sparkling wines

The influence of pre-fermentative maceration and ageing factors on the ester profiles of Pedro Ximenez sparkling wines was evaluated. The pre-fermentative maceration consisted of the skin-maceration of musts at 10 degrees C for 6 h. The sparkling wines were produced following the Champenoise method. Samples were monitored at 3, 6 and 9 months of ageing on lees. Sparkling wines with pre fermentative maceration displayed higher contents of ethyl esters of branched acids and cinnamates. Meanwhile, those without maceration showed higher levels of ethyl esters of fatty acids and higher alcohol acetates. The study of statistical interactions elucidated different hydrolytic kinetics and developments in higher alcohol acetates and ethyl esters of branched acids during ageing. The application of a dual criterion based on univariate (ANOVA) and multivariate analyses (OPLS-DA) allowed us to identify new potential volatile markers related to pre-fermentative maceration and ageing time, reported for the first time in sparkling wines

Status and conservation of old-growth forests and endemic birds in the pine-oak zone of the Sierra Madre occidental Mexico

The pine-oak forests of the Sierra Madre Occidental, a mountain range in NW Mexico, have recently been recognized as an area of high endemism and biodiversity. Selective logging threatens three bird species endemic to this habitat, who depend on standing dead trees (snags). This report is based on an 11 month field survey that aimed to locate oldgrowth remnants and to assess the status of the endemic birds. Old-growth is defined here as a forest that has never been logged mechanically. Old-growth forests were located by ground-truthing of areas predicted by various methods: analyses of topographical maps and satellite images, aerial surveys, interviews with forestry technicians and local inhabitants, and literature studies. None of the prediction methods gives unambiguous results on their own. Only by applying the whole set of techniques could a comprehensive inventory be obtained of old-growth sites. Of the original 93, 560 km² of pine-oak habitat in the Sierra Madre Occidental, 571 km² remained as old-growth in 1995. This is a reduction of 99.4 %. The forests on high mesas, where the largest and most accessible timber stood, have been reduced to 22 km² uncut forest. In logged forests pines greater than 30 cm girth have been extracted and snags have been cut for the production of paper pulp. Small settlements are everywhere. Information on the Imperial Woodpecker Campephilus imperialis was obtained through interviews with 62 elder inhabitants who had known the bird. The extinction peak of this species was between 1946 and 1965, when 60 % of the informants saw their last Imperial Woodpecker. Hunting by settlers and loggers, for fun and for medicinal purposes, quickly decimated populations. Recovery from the shooting became impossible through the ensuing logging of nearly all the pine-oak habitat. Mature pines and pine snags were removed, depriving the Imperial Woodpecker of foraging and nesting sites. Imperial Woodpeckers were often seen in groups. A typical group consisted of seven or eight birds. With an estimated average density of one Imperial Woodpecker per 13 km², the original pine-oak habitat in the whole range of the species may have carried only 8,000 individuals or 1060 groups. Interviews, and workings found in one old-growth area, indicate that very few Imperial Woodpeckers may have survived into the 1990s. Extinction of the species seems nevertheless inevitable since nowhere does any breeding habitat remain. Cutting of snags is the main threat to the Thick-billed Parrot Rhynchopsitta pachyrhyncha. This species only breeds at altitudes above 2300 m, but snags are scarce on the exploited mesa forests in the highest parts of the sierra. The breeding range runs from within 85 km of the US border in northern Chihuahua south to central western Durango, with an apparent gap in southern Chihuahua. Pine seeds for foraging are widely available in young recovering forest. Compared with historical records, encountered groups of wintering Thick-billed Parrots were small, few groups were seen, and the numbers of bathing and drinking parrots at a waterfall in northern Chihuahua were low. This indicates numbers have sharply declined in the course of the 20th century. The status of the Eared Trogon Euptilotis neoxenus is far less critical. Eared Trogons were observed at 55 locations, mainly in canyons. Nests were found in riparian corridors in canyons. Such corridors are hardly accessible to the logging industry. The ability, and probable preference, of the Eared Trogon to breed in canyons likely explains why it is still fairly common. The erroneous notion that the Eared Trogon is a local and rare species must stem from the paucity of field studies in the Sierra Madre Occidental, as well as the wariness of the bird. It is mostly to be detected by its vocalizations. Efforts are being made to ensure the total protection of three priority areas (figures 26 to 28). These areas encompass the main old-growth fragments in the Sierra Madre Occidental. They are also of major importance to the endemic fauna. Protection of snags is required for three breeding areas of the Thick-billed Parrot (figures 29 to 31). Ideally, exploitation of snags should be banned throughout the Sierra Madre Occidental

Novel probabilistic optimization model for lead-acid and vanadium redox flow batteries under real-time pricing programs

The integration of storage systems into smart grids is being widely analysed in order to increase the flexibility of the power system and its ability to accommodate a higher share of wind and solar power. The success of this process requires a comprehensive techno-economic study of the storage technology in contrast with electricity market behaviour. The focus of this work is on lead-acid and vanadium redox flow batteries. This paper presents a novel probabilistic optimization model for managing energy storage systems. The model is able to incorporate the forecasting error of electricity prices, offering with this a near-optimal control option. Using real data from the Spanish electricity market from the year 2016, the probability distribution of forecasting error is determined. The model determines electricity price uncertainty by means of Monte Carlo Simulation and includes it in the energy arbitrage problem, which is eventually solved by using an integer-coded genetic algorithm. In this way, the probability distribution of the revenue is determined with consideration of the complex behaviours of lead-acid and vanadium redox flow batteries as well as their associated operating devices such as power converters