In this paper we introduce NSLoadGen (Notification Services Load Generator), a testbed platform that supports the definition of real-life scenarios, the simulation of these scenarios against notification services, and finally generating vast data that can be used to precisely evaluate it. NSLoadGen is not targeted at any specific Notification Services, but rather is generic and adaptable. It has been designed to support a wide variety of Notification Services characteristics, hiding the many differences among messaging products/specifications (e.g. Java Message Service [1]) and, at the same time, it is easily extensible to support new implementations. This paper covers the different steps the tool follows (scenario definition, scenario simulation and result collection), the proposed approach, as well as relevant design and implementation details.