Testing IoT devices poses significant challenges, especially due to the need for real hardware to accurately simulate device interactions in real-world environments like smart homes. Unlike traditional software, which can often be tested in virtual settings, IoT systems rely on physical setups to account for critical factors such as network behavior, interoperability, and real-time responses. This dependency on actual devices increases costs and limits scalability, making it difficult to conduct large-scale, comprehensive tests across complex IoT networks. This thesis addresses this problem by designing and developing a simulator specifically for Commercial-Off-The-Shelf (COTS) smart devices, focusing on the second generation of Shelly devices.