With a continuously growing share of non-dispatchable renewable energy sources in the power mix, flexibility in hydropower provision is becoming fundamental. The major role played by hydropower in frequency regulation in the last years has underlined the possible drawbacks of fast regulation impacting the hydraulic system health. Two of the most promising solutions to address this problem are the hybridisation of hydropower with battery energy storage systems and the variable speed technology. Batteries have already proved to be able to provide multiple services to the power system, and their coupling with hydropower is a possible interdisciplinary solution to increase flexibility provision in power systems. In this respect, one of the main challenges to address is the control of the hybrid system. While research is heading towards this direction, it becomes necessary to have experiment facilities able to test and validate the upcoming solutions. Testing platforms are nowadays decoupling the hydraulic and the electric components, testing them separately, therefore, they are not suitable for the validation of the control strategy under real grid conditions. The scope of this paper is to present an experimental facility where different joint control techniques can be tested on reduced scale models of hydraulic machines hybridized with a battery energy storage system. The presented test-rig combines all the fundamental components, both on the hydraulic and on the electrical side, within the same testing facility. The platform is an adaptation of the already existing laboratory of hydraulic machines at EPFL in Switzerland.