A testing device for testing a distance sensor includes: a receiver for receiving an electromagnetic free-space wave as a receive signal; an analog-to-digital converter configured to, in a simulation mode, convert the receive signal into a sampled signal; a signal-processing unit configured to: delay the sampled signal or a modulated sampled signal to form a delayed sampled signal or a modulated delayed sampled signal; and modulate, upon the sampled signal or upon the delayed sampled signal, a predeterminable Doppler signature as a characteristic motion profile of a reflecting object to be simulated to form the modulated sampled signal or the modulated delayed sample signal; a digital-to-analog converter configured to convert the modulated or the modulated delayed sampled signal into a simulated reflected signal; and a transmitter configured to radiate the simulated reflected signal or a simulated reflected signal derived from the simulated reflected signal as an output signal.