The security of SCADA systems is a major concern. Indeed, these systems are used to manage important infrastructures. However, conducting security analyzes on these systems is almost impossible. Therefore, using simulators is the best way to do that. In this paper, we describe our simulator for WirelessHART SCADA-based systems. It implements the whole protocol stack and both field devices and the Network Manager including routing and scheduling algorithms. The simulator is specially tailored to assess WirelessHART security mechanisms and to test attacks and countermeasures. It includes scenarios for testing several kinds of attacks such as sybil and denial of service (DoS) attacks. Also, new scenarios can easily be added to test other kinds of attacks.