I assume you plan to do the "crawl method" for determining best placement. In theory, the orientation doesn't matter since the wavelengths are magnitudes larger than the sub cabinet, thus omnidirectional. However, if you're placing the sub on a chair or sofa, I would fire the driver/ports away from any padding in case it wants to act as a bass trap.
There are many different sub designs, but they always have a "front" which is usually facing into the room. Where the TV is really has no bearing. It's more where the listeners are.
EDIT: now I see more what you are asking. You basically want to reverse everything from the final setup, so, in general, you want it facing into the room, or the opposite direction it will be facing in the final installation.