A system for testing a control system in a vessel, comprising: sensors on board the vessel; command input devices on board the vessel to send desired position, course, velocity; an algorithm in the control system for the computation of control signals to the vessel actuators; communication lines for sending simulated command signals from a remote test laboratory to the control system; a simulator including an algorithm for the simulation of the new dynamic state of a vessel model based on a previous state; where the communication line is arranged for sending back the new simulated stare of the vessel model in the form of simulated sensor signals for continued computation to achieve desired position, course, velocity; and where the communication line is sending the response from the control system to the remote test laboratory.