We report the development of a comprehensive firmware validation system for the Level-0 (L0) Endcap Muon Trigger in the HL-LHC ATLAS experiment. We aim to achieve systematic and efficient firmware validation through a comprehensive study across hardware, software, and databases. The system tests various inputs, including benchmarking artificial track data, full-simulation, and collision data. Our design of the validation system enables systematic tests by injecting identical dataset in the software simulation environment and actual hardware testbench coherently, which enables a direct event-by-event comparison. Along with the system's design, we have developed a relational database to centrally manage cabling information and data format, as well as a bit-wise trigger algorithm simulator, aiding firmware debugging and improvement.