If your goal is to simulate a universe where there is one person, and a glowing cube, and empty space everywhere else in the universe, this is a great test.  Otherwise no.  You could set the maximum number of bounces and you'd still get a decidedly odd result.  At the very least, you must have a polygonal ground plane, and then you'd have a universe of a single person standing on a perfectly flat floor.

GI light does not bounce off of air.  If the only thing in your scene is the one character and maybe the light-emitting surface, nearly all the rays emitted by the light will hit the character once and then vanish off into the empty universe.  You need a polygonal environment to render in.  If you're trying to simulate indoor light, then a cube is a good place to start.  All this testing you're doing will be dramatically different from what you'd get once you place the character in a room or, if outdoors, near the ground or some structures.

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