MQTT is a Client Server publish/subscribe messaging transport protocol. It is lightweight, open, simple and designed to be easy to implement. These characteristics make it ideal for use in many situations, including constrained environments such as communication in Machine to Machine (M2M) and Internet of Things (IoT) contexts where a small code footprint is required and/or network bandwidth is at a premium. MQTT Server Test Suite is designed to act as a malicious MQTT Client. It can be used to test MQTT servers (brokers) and clients to find security flaws and robustness problems. The test suite contains test cases for testing MQTT protocol specific operations. Additionally the test suite can be configured to test MQTT application layer specific payload which goes over the MQTT protocol.