I usually wear a simple (cheap), understated, dress for moves tests. However, for Senior, I gave coach a choice between 2 show dresses and a plain purple dress and she said one of the two show dresses. I have a dress that I would have loved to wear, but I don't have the time, money, or the actual stones to do it the way I want to (I want to do fire opals, and I currently don't own any in the size I want).
The two show dresses, while flashy, are appropriate for a Senior test, I think.
But at the pre-Bronze level, a simple (cheap) dress or leggings (in pristine condition) and a wrap skirt should be fine. When in doubt, ask your coach what the expectation and unwritten rules at your club, and the club you are testing at are.