RELAI Testing: A Technique to Assess and Improve Software Reliability

Testing software to assess or improve reliability presents several practical challenges. Conventional operational testing is a fundamental strategy that simulates the real usage of the system in order to expose failures with the highest occurrence probability. However, practitioners find it unsuitable for assessing/achieving very high reliability levels; also, they do not see the adoption of a “real” usage profile estimate as a sensible idea, being it a source of non-quantifiable uncertainty. Oppositely, debug testing aims to expose as many failures as possible, but regardless of their impact on runtime reliability. These strategies are used either to assess or to improve reliability, but cannot improve and assess reliability in the same testing session. This article proposes Reliability Assessment and Improvement (RELAI) testing, a new technique thought to improve the delivered reliability by an adaptive testing scheme, while providing, at the same time, a continuous assessment of reliability attained through testing and fault removal. The technique also quantifies the impact of a partial knowledge of the operational profile. RELAI is positively evaluated on four software applications compared, in separate experiments, with techniques conceived either for reliability improvement or for reliability assessment, demonstrating substantial improvements in both cases.