As simulation-based, mixed-reality, and virtual reality training systems are more widely adopted in the military, the process of verification and validation (V&V) for these systems becomes similarly more complicated and timeconsuming. It is critical to verify and validate these simulation-based training systems so they operate properly and as expected. Often, live trainees are brought in, hardware set up, and different configurations of a system tested as part of the V&V process. No actual training has occurred. In much the way that these simulation systems act as a substitute for live action, the subsystems and trainees that use training systems can also be replaced with simulations to dramatically speed-up V&V. This paper examines the potential for replacing live trainees and hardware with virtual simulations in a mixed-reality training environment for the purposes of V&V of a simulation training system. ! A case study is presented, composed of a method that allows multiple tracking systems, from different vendors, to be combined into a single system. The system, used in a large mixed-reality training environment, allows different aspects of the physical layout to be tracked depending on the training being performed. In order to test the system's robustness, virtual tracking data was generated, having been calibrated from actual tracked entities, to test metrics including positional error correction and data throughput capability. Comparing this data with results obtained using real tracking hardware allowed the development of models to predict the system's behavior in new situations, such as the introduction of a new tracking system, or introducing a second tracked space to the training simulation. Using simulated tracking data, errors were identified in the system without the need for testing with humans or additional equipment. Finally, the virtual data was used to test the simulation itself, to ensure it would handle the data requirements encountered during actual training. Results indicated that simulated data can be used to test the various factors necessary for V&V of a simulation-based training system. The training system behavior was the same whether actual or simulated data was used. The use of simulated data allowed scenarios to be tested without the need to bring in additional human and equipment resources.