Testing refinements by refining tests

One of the potential benefits of formal methods is that they offer the possibility of reducing the costs of testing. A specification acts as both the benchmark against which any implementation is tested, and also as the means by which tests are generated. There has therefore been interest in developing test generation techniques from formal specifications, and a number of different methods have been derived for state based languages such as Z, B and VDM. However, in addition to deriving tests from a formal specification, we might wish to refine the specification further before its implementation. The purpose of this paper is to explore the relationship between testing and refinement. As our model for test generation we use a DNF partition analysis for operations written in Z, which produces a number of disjoint test cases for each operation. In this paper we discuss how the partition analysis of an operation alters upon refinement, and we develop techniques that allow us to refine abstract tests in order to generate test cases for a refinement. To do so we use (and extend existing) methods for calculating the weakest data refinement of a specification

Formal Specification and Testing of a Management Architecture

The importance of network and distributed systems management to supply and maintain services required by users has led to a demand for management facilities. Open network management is assisted by representing the system resources to be managed as objects, and providing standard services and protocols for interrogating and manipulating these objects. This paper examines the application of formal description techniques to the specification of managed objects by presenting a case study in the specification and testing of a management architecture. We describe a formal specification of a management architecture suitable for scheduling and distributing services across nodes in a distributed system. In addition, we show how formal specifications can be used to generate conformance tests for the management architecture

Use of Roadside Deer Removal to Reduce Deer–Vehicle Collisions

Identification of management tools to reduce the incidence of deer–vehicle collisions (DVCs) is important to improve motorist safety. Sharpshooting to reduce white-tailed deer (Odocoileus virginianus; deer) along roads has proven successful in urban situations but has not been evaluated in undeveloped areas. We used a before-after-control-impact (BACI) design to evaluate the use of sharpshooting to reduce DVCs along roads on the uninhabited U.S. Department of Energy’s Savannah River Site, South Carolina, USA, during 2011–2017. We removed 242 deer from 4 treatment roads during 2015 and 2016, with 2-year removal rates per road averaging 5.0 deer/km of road (range 4.0–5.8). We monitored accident rates as DVCs per million vehicle-km traveled (VKT) during annual cycles (March–February) following the initial removal and during the 7 months (March–September) following removals in spring and the 5 months (October–February) following removals in fall. The response in accident rates varied among the annual cycle, spring, and fall. The BACI effect indicated that removal treatments reduced accident rate by 1.184 DVCs per million VKT (P = 0.081) over the annual cycle and by 1.528 DVCs per million VKT (P = 0.023) following spring removals, but following fall removals we detected no effect (P = 0.541). Relative to the pre-removal accident rate for removal roads, the estimated treatment effect on an annual basis equated to a 39.4% reduction in accidents and during spring equated to a 50.8% reduction in accidents. We conclude that sharpshooting along roads in undeveloped areas can be a viable tool to reduce DVCs and can be useful in areas where population control via hunter harvest is not practical or desirable

Major complication after intrauterine vesico-amniotic shunting

Bilateral foetal uropathy is the leading cause of chronic renal failure in childhood. Vesico-amniotic shunting (VAS) is a simple, feasible, and widely used procedure for decompressing the foetal urinary system. We report acase of a boy with bilateral foetal uropathy who underwent VAS at a gestational age of 29 weeks. Vesico-abdominal shunt dislodgement occurred and led to urinary ascites and anhydramnios. Postpartal laparotomy showed ashunt perforation between the urinary bladder and the peritoneal cavity