In this paper, we present a number of state-of-the art methods for testing power system controllers based on the use of a real-time power system simulator. After introducing Hypersim, we list and discuss the different means of connection between the controller under tests and the power system simulator. We then present two applications based on this method. The first one is an agent based controller used to increase the penetration of wind energy in a weak grid, and the second one is the controller of a gas micro turbine connected to the distribution grid.Index Terms-Agent-based systems, Controller testing, Hardware-in-the-loop, Real-time simulation.