High-coverage testing of sensornet applications is vital for pre-deployment bug cleansing, but has previously been difficult due to the limited set of available tools. We integrate the KleeNet symbolic execution engine with the COOJA network simulator to allow for straight-forward and intuitive high-coverage testing initiated from a simulation environment. A tight coupling of simulation and testing helps detect, narrow down, and fix complex interaction bugs in an early development phase. We demonstrate the seamless transition between COOJA simulation and KleeNet symbolic execution. Our framework enables future research in how high-coverage testing tools could be used in cooperation with simulation tools.