Using SimpleIoTSimulator (SimpleSoft - Using SimpleIoTSimulator as a LoRaWAN Network Simulator) you can simulate hundreds of LoRa gateways and sensors to test Network and Application Servers prior to deployment.
Devices support LoRaWAN 1.0.3 and 1.1 specifications with OTAA and ABP activation methods. Gateways support BasicStation and Semtech UDP packet forwarding when communicating with designated Network Servers.
A short 4 min Youtube video highlighting the use of the simulator with ChirpStack Network Server is available at Using SimpleIoTSimulator for Testing LoRa ChirpStack Network Server - YouTube