Modeling the impact of testing on diverse programs

Abstract

This paper presents a model of diverse programs that assumes there are a common set of potential software faults that are more or less likely to exist in a specific program version. Testing is modeled as a specific ordering of the removal of faults from each program version. Different models of testing are examined where common and diverse test strategies are used for the diverse program versions. Under certain assumptions, theory suggests that a common test strategy could leave the proportion of common faults unchanged, while diverse test strategies are likely to reduce the proportion of common faults. A review of the available empirical evidence gives some support to the assumptions made in the fault-based model. We also consider how the proportion of common faults can be related to the expected reliability improvement.