John H. R. May

Software unit test coverage and adequacy

Objective measurement of test quality is one of the key issues in software testing. It has been a major research focus for the last two decades. Many test criteria have been proposed and studied for this purpose. Various kinds of rationales have been presented in support of one criterion or another. We survey the research work in this area. The notion of adequacy criteria is examined together with its role in software dynamic testing. A review of criteria classification is followed by a summary of the methods for comparison and assessment of criteria.

Reliability estimation from appropriate testing of plant protection software

Plant protection software may be realistically tested using inputs from a plant model before its initial use, or when it is not feasible to take the plant into certain fault conditions. The process of testing to estimate a software reliability is illustrated, including simulation of the software input space and statistical inference from test results to a reliability estimate. In addition to a conventional statistics approach to this problem, a new statistical model is presented which has been developed within a program of Nuclear Electric research into software reliability testing.

Inductive Inference and Software Testing

The term ‘inductive inference’ denotes the process of hypothesizing a general rule from examples. It can be considered as the inverse process of program testing, which is a process of sampling the behaviour of a program and gathering confidence in the quality of the software from the samples. As one of the fundamental and ubiquitous components of intelligent behaviour, much effort has been spent on both the theory and practice of inductive inference as a branch of artificial intelligence. In this paper, software testing and inductive inference are reviewed to illustrate how the rich and solid theory of inductive inference can be used to study the foundations of software testing.

A model of code sharing for estimating software failure on demand probabilities

A statistical software testing model is proposed in which white box factors have a role. The model combines test adequacy notions with statistical analysis, and in so doing provides a rudimentary treatment of dependencies between test results caused by the execution of common code during the tests. The model is used to estimate the probability of failure on demand for software performing safety shutdown functions on large plants and concerns the case where extensive test results are available on the latest version of the software, none of which have resulted in software failure. According to the model, there are circumstances in which some current statistical models for dynamic software testing are too conservative, and others are not conservative, depending on the software architecture. >

Nuclear Electric’s Contributions to the CONTESSE Testing Framework and its Early Application

The various areas of study undertaken by Nuclear Electric for their contributions to the CONTESSE project are briefly listed. One of these areas, methods for statistical software testing, is then reported more fully, after its role in the UK’s safety principles for nuclear power plants has been identified. Appropriate techniques for statistical testing of plant protection systems are detailed.

Injecting Faults into Environment Simulators for Testing Safety Critical Software

Software testing via environment simulation is an approach to testing safety critical software. By this approach, to test software in adverse conditions we need to simulate the failure processes of the environment system. Such testing is essential for safety critical software, especially for protection software. However, due to the complexity of failure processes, the development of simulators of failure processes is complicated, expensive and difficult. This paper presents a method to derive such simulators systematically and efficiently. The basic idea is to inject faults into the simulator of the healthy environment system to obtain the simulators of faulty environments.