Model-driven engineering (MDE) techniques are increasingly being used to address many of the development and operational lifecycle concerns of large-scale component-based systems. One such concern that is growing in importance, but lacking significant research is the validation of quality-of-service (QoS) properties of component-based systems throughout their development lifecycle. In the current state of the art, large-scale component-based systems have to wait until system integration time to perform in-depth QoS testing, which can be too late and detrimental to project schedules and costs. This paper describes our novel MDE-based solution to address this challenge. At the core of our solution approach are (1) a set of domain-specific modeling languages that allow us to mimic component "business logic," and (2) a generative programming framework that synthesizes configuration files for system simulation. A particular thrust of this paper is describing the syntax and semantics of the component behavior modeling language, which are based on the Input/Output automaton formalism. Our experience shows that our techniques enable developers of large-scale component-based systems to perform early QoS evaluation from development time to production time. Moreover, our experience shows we are able to provide an environment where developers can rapidly test ideas and methodologies largely alleviating the need to expend effort, money, and time implementing them. © 2007 ACADEMY PUBLISHER.