Rapid prototyping of a Networked Control System (NCS) is challenging because of the physical distribution of agents. Furthermore, experiments with NCS may be subject to external influences which prevent reproducibility. This article presents an architecture for experimental testing of NCS with focus on decision-making. Our architecture for experiments of NCS is strictly modular and hierarchical, and therefore it supports an easy and rapid exchange of each single controller as well as of optimization libraries. Additionally, the architecture synchronizes the whole network of sensors, computation devices, and actuators. Thus, it achieves deterministic and reproducible results, even for time-variant network topologies. Using this architecture, we are able to include active and passive agents and agents with heterogeneous dynamics in the experiments. The architecture also allows handling communication uncertainties, e.g., data packet drop and time delay. The resulting architecture supports performing in-the-loop tests on the model, software, and hardware levels. We demonstrate the architecture in the Cyber-Physical Mobility Lab (CPM Lab) using 20 agents. The architecture can be applied to other domains.