The entire world is moving towards the era of smart technology. Internet of Things (IoT) is the key factor behind this revolutionary change. A simple IoT system comprises a device or thing with embedded sensors, which are connected to an application through the internet. The thing or device can be remotely controlled and monitored from anywhere in the world through the internet. Due to this feature, it has been applied in various domains like home automation, Patient health monitoring, agricultural sector, environment surveillance and much more. Due to the increased usage of IoT based systems, there arises a need for validating and verifying the devices in all aspects. Though different IoT developers follow their own methodologies to test their IoT device, there is a need for a generic test model for validating IoT applications. We propose a test model for testing an IoT system by integrating the existing test models for software, hardware and communication protocols. We evaluated our model by executing a case study for Intrusion Detection System (IDS) using IoT. Experimental evaluation proves that this model can be used as a reference model for IoT developers for evaluating the performance and capabilities of an IoT system.