This trick works in Test Drive mode with any car on any track with a pit. Enter the pit, then pause game play. Go to the "Tune Car" option. As soon as it appears, press A to return to the pause menu. Resume the game. You should now be able to drive around the pits freely. If you have damage on and you exit the pits backwards, you will not take any damage (even if it appears that you are).

When in Test Drive mode and you are in the pit, select "Tune Car". Go out of the menu. Back straight out of the pit. The message "Pitting" will still appear, and you will be able to drive around and crash your car without any taking any damage, except for your car getting scratched up, etc.