A device for integrity testing a system for rapid reactivation of a turboshaft engine of a helicopter, includes a pneumatic turbine that is mechanically connected to the turboshaft engine and is supplied with gas, upon a command, by a pneumatic supply circuit such that it is possible to rotate the turboshaft engine and ensure that it is reactivated. The testing device has an apparatus configured to withdraw pressurized air from the turboshaft engine and a duct for conveying the withdrawn air to the pneumatic circuit for supplying the pneumatic turbine with gas. The device further includes a sensor for determining the rotational speed of the pneumatic turbine.