: In a component testing approach for evaluating system reliability, one tests units of the components or subsystems that make up a larger system in order to draw conclusions about the reliability of the latter. An optimum, system-based component test plan explicitly account for the relationship between component and system reliabilities and also minimizes total testing effort. This paper reviews the main features of such plans and describes an application to reliability testing of a software system that is made up of several different components/modules.