Robotic ecologies are networks of heterogeneous devices (sensors, actuators, automated appliances and mobile robots) pervasively embedded in everyday environments, where they cooperate to the achievement of complex tasks. Their successful application opens important research questions for both their engineering and their interaction with human users. In this paper we illustrate a testbed built to support interaction studies between human users and robotic ecologies. The testbed consists of an interactive and autonomous robotic ecology that is able to engage with human users, react to their activities, and even introduce them to the main concepts behind robotic ecologies. We describe how such a testbed is built using a middleware purposefully designed for robotic ecologies, and we report our experiences in its application to a number of project demonstrations and human-robot interaction studies.