The NB-IoT NTN System Test Bench (STB) is a cost-effective, flexible testing environment for NB-IoT NTN eNodeB product developers. Simulating either transparent or regenerative modes for LEO satellite networks, customers can take advantage of provided test scenarios or develop their own. MEO and GEO capabilities will be supported in the future. The STB simulates a population of UE devices within a specific geographical area, corresponding to the single beam area of a satellite, communicating with a server application using highly customisable data flows to represent IOT like behaviour. The data flows will be assessed over the different test configurations to show the effects of varying NTN related parameters, such as satellite trajectories, beam sizes and constellation densities and NTN channel impairments. NB-IoT NTN eNodeB product developers can easily analyse system performance and degradation experimentally, saving potentially millions of dollars.