1. A method is provided for in-place testing of Time Triggered Ethernet (TTE) command and control (C&C) system having real input devices and output interfaces that communicate through one or more switches during first predetermined time intervals set by a time scheduling system associated with the C&C system as to when outputs from the real input devices can be sent to the output interfaces, comprising: providing a simulation subsystem having therein simulated input devices adapted to provide predetermined or dynamically calculated outputs mimicking the outputs of the real input devices and communicating with the output interfaces through at least a further switch during second predetermined time intervals set by a time scheduling system associated with the simulation subsystem system as to when outputs from the simulated input devices can be sent to the output interfaces; and adjusting the second predetermined time intervals relative to the first predetermined time intervals, so that the outputs from the simulated input devices arrive at the output interfaces prior to the outputs from the real input devices.