Hrm it is a bit funny that modern cars are drive-by-wire (at least for throttle) and yet they still require a skilled driver to follow a speed profile during testing, when theoretically the same thing could be done more precisely by a device plugged in through the OBD2 port.
You need to remove your shoe and drive with like two toes to get the speed just right, though.
Test drivers I have done this with takes off their shoes or use ballerina shoes.