Abstract: Software development for Wireless Sensor Networks (WSNs) is challenging due to characteristics of sensor nodes and the environment they are deployed in. Testing software in a real WSN testbed allows users to get reliable test results. However, real testbeds become more expensive as the number of sensor nodes in the network grows. Simulation tools are alternatives to real testbeds. They are cheaper, faster and repeatable. However, simulation results are not reliable as that of testbeds. Therefore, there is a need for a testing tool that can leverage the advantages of testbeds and simulation tools. These tools are usually called hybrid simulators. In this survey, we discuss several hybrid simulators that use real sensor motes integrated with a simulator to make software development cheaper, repeatable and to make the results more reliable.