Welcome to the forum there! The thing is too easy, it even doesn't need BGT to work, just a sound editor and the words left and right (center can also be added). You then have to put each one in its appropriate channel as well as a sound of a certain something rotating from far left to far right. Doing speaker tests can be as simple as recording the words left and right and putting them in their channels, and it can also be something advanced if you have some creativity and an experience in sound designing. At the end, put the resulting sound file in your project and add a menu option which plays it. Note that you can do the same things in different ways including the soundpool function, but the one I mentioned is the easiest I suppose.
Regards!