Unmanned aerial system (UAS) use is ever-increasing. In this paper, it is shown that even with low-cost hardware and open-source software, simple numerical testing practices (software- and hardware-in-the-loop) can prove the accuracy and usefulness of an aeronautical flight model, as well as provide valuable pre-flight testing of many situations typically only encountered in flight: high winds, hardware failure, etc. Software and hardware simulation results are compared with actual flight testing results to show that these modeling and testing techniques are accurate and provide a useful testing platform for a small unmanned aerial vehicle. Source code used in simulation is open and provided to the community.