This document introduces the Signal Application Testing System (SATS) developed by Princeton Consultants, a robust simulation tool that improves and substantially automates rail system testing. SATS automates many tests and finds errors that may have been missed during manual assessment. SATS users find 80% or more of software errors during simulation. The system is easy to configure, set up and use, and can be set up in less than 3 minutes per asset. It also automatically sets up locations and performs automated testing. SATS is fully integrated with PTC applications and is frequently updated with new features and compiler support.