We present a large-scale distributed environment for Peer-to-Peer (P2P) software. It enables developers to run and debug their P2P software written in Java using the JXTA framework with minimal effort: Via a web frontend to the central server they can easily setup a JXTA P2P network on a large number of computers at different physical locations and upload their code. By only one mouse click they can trigger an automated configuration, start / stop / reset their test scenario, and view debug output. For this purpose the central server holds the complete configuration of the environment, and automatically controls, configures, and updates all computers of the environment. Except for the server, no dedicated hardware is required; rather, our environment can be installed on existing Windows and Linux computers, where it runs with lowered priority in order not to disturb other users / processes. There is no prescribed limit on the number of computers being part of the environment; its current setup for the EU FP6-IST project AEOLUS, for example, consists of more than 100 computers at 13 different locations in Europe. By virtualization the number of peers can be increased by a factor of up to 10. Further computers, which, e.g., may act as a frontend to the P2P software or as a gateway to special hardware such as sensor networks, can easily be integrated. Finally, our environment is secured against both external attacks over the Internet and internal attacks via hijacked accounts or malfunctioning software.