We present a novel, easy to use virtual testbed enabling researchers to evaluate their localization algorithms based on distance measurements in indoor environments. We provide precise ground truth information collected by our previously presented reference system, based on a mobile robot, in combination with range measurements from a Wireless Sensor Network (WSN) in multiple buildings. The user can define a virtual experiment using our datasets over the web. This approach separates the process of designing a robust indoor localization algorithm from the need for testing it on actual hardware in different scenarios.