Last week, we had the author of TDD for a Shopping Website LiveProject. Friday at 11am Ranch time, Steven Solomon will be hosting a live TDD session just for us. See for the agenda and registration link
Agree with Mohammed earlier. You want a JDialog, which disappears after use. Much better than trying to create two frames and dispose of the second.
Actually, you can probably use the setDefaultCloseOperation method on the frame, with DISPOSE_ON_CLOSE, so the dispose() call may be unnecessary.