Embodiments described herein extend to methods, systems, and computer program products for setting up, configuring, and customizing one or more virtual machines. A scenario definition file may be accessed and parsed to provide information to a virtual machine provisioning server. A virtual machine is provisioned and instantiated according to the information contained in the scenario definition file. A virtual machine is instantiated upon a host machine. Upon instantiation, a virtual machine communicates with a custom action service to execute an action upon the virtual machine.