This article presents a platform for flexible hardware- and model-in-the-loop integration of driver assistance systems in a driving simulator environment. The new platform combines the capabilities of a full-scale vehicle electrical systems test environment with the driver interaction evaluation capabilities of an advanced driving simulator. This enables faster development cycles for driver assistance systems by allowing easy transition between simulation configurations used in the development process (e.g. Software-in-the-Loop and Hardware-in-the-Loop) and, crucially, includes the driving simulator as a key part in all stages of the process. The presented integrated test environment enables easy and fast adaptation to include different driver assistance systems of varying degrees of development maturity and functional integration in an advanced driving simulator. Generic interfaces guarantee flexibility and the architecture enables scalability of the development environment for new functions, ranging from desktop simulation to advanced driving simulators. In this integrated test facility even complex interactive full system tests of potential dangerous scenarios can be easily repeated. As an example a test scenario for a system with autonomous steer intervention will be presented and discussed.