Testing on system level using a static and homogeneous architecture of clients is common practice. This paper introduces a new approach to use a heterogeneous and dynamic set of resource restricted test clients for automated testing. Due to changing resources and availability of the clients, the test case distribution needs to be recalculated dynamically during the test execution. All necessary conditions and parameters are represented by a formal model. It is shown that the algorithmic problem of DYNAMIC TESTPARTITIONING can be solved in polynomial time by a heuristic recursive algorithm. A testbench architecture is introduced and by simulation it is shown that the testbench can execute the test requirements within a small variation using a number of several hundred clients. The system can react dynamically on changing resources and availability of the test clients within several seconds. The approach is generic and can be adapted to a huge number of systems.