Other forms: dress rehearsals
When you're preparing for a live performance, your last practice session will probably be a dress rehearsal, with all of the performers wearing the costumes or outfits they'll wear during the actual event.
In the theater, a dress rehearsal gives the actors a chance to say their lines and hit their marks one last time before opening night. It's called a dress rehearsal because performers wear their full costume and makeup, dressed just as they will be during the performance. You can also use this term figuratively, for anything you're trying out: "Before the first day at our new school, let's have a dress rehearsal and walk over there to make sure we know the way."