I have owned one of these mini light testers for 3 seasons now and I can't say how much I love it! Anyone out there who uses a lot of mini lights and has problems with strings that go half out and you can't find the cause...this is the remedy. There were times when I had a section of tree trunk go dark and all I had to do was plug the sting into this thing and hit the botton. Either the bad bulb would buzz or the entire string would light again like magic.
It's a little pricy, but it is worth its weight in gold. I thought I would tip off others on this board to it. If you had mini lights driving you crazy this year, maybe you can start dropping hints now for your birthday.