Determining Component Reliability Using a Testing Index

Component-Based Software Engineering has the potential to provide reliable systems based on tested components quickly and economically, but these systems will only be as reliable as the components from which they are constructed. We propose a 6-point scale which can be used to rate the degree to which a component has been tested. This scale can be used by developers to assess the risk of using a third party component. Since a variety of test strategies are used, it is necessary to correlate testing strategies with our scale. In this paper, we examine the testing strategies specified in British Standard 7925-2 and show how they relate to the reliability levels that we propose. Since well-behaved use of resources is also a key factor in overall system reliability, we propose that an 'R' tag be added to the rated level when resource usage has been verified to be within reasonable bounds.