Effect of repair policies on software reliability

Software reliability is an important metric that quantifies the quality of the software product and is inversely related to the number of unrepaired faults in the system. Fault removal is a critical process in achieving the desired level of quality before software deployment in the field. Conventional software reliability models assume that the time to remove a fault is negligible and that the repair process is perfect. We examine various kinds of repair scenarios, and analyze the effect of these fault removal policies on the residual number of faults at the end of the testing process, using a non-homogeneous continuous time Markov chain. The fault removal rate is initially assumed to be constant, and it is subsequently extended to cover time and state dependencies. These fault removal scenarios can be easily incorporated using the state space view of the non-homogeneous Poisson process.