Well, Deep THOUGHT you certainly live up to your name. I agree with you 100%, it was indeed a test for Luke to face his darkside and the fact that he was linked to Vader and the fact that he could become the next Vader if he wasn't careful. Of course Luke failed the test and the way he failed was that yoda just got through telling him, "a Jedi uses the Force for knowledge and defense, NEVER for attack". As soon as Luke saw the Dark Lord in that cave, he drew his sabre 1st, which constituted an agressive attack {anger, fear, agression, the dark side are they} the moment Luke drew his sabre 1st, he failed the test.
when he was fighting in the cave he was geeting more and more angry
and remember what yoda said too anikan in ep 1 'fear is the path to the dark side... ...anger leads to hate...' and darths helmet exploded and he see's himself in there, i think this is yoda saying to luke, that if he keeps these emotion anger, revenge, he will most certaimley end up in the dark side.
LUKE: There's something not right here. I feel cold, death.
YODA: That place...is strong with the dark side of the Force. A domain of evil it is. In you must go.
LUKE: What's in there?
YODA: Only what you take with you. Your weapons...you will not need them.
teehee! sorry, I'm in my looking-up mood right now!
so... anything else now? *jumps up and down, with big star wars book in mouth*