You can keep the tester in your very smallest pocket..
Take a careful look at Battery caused LED brightness.
And there are other uses for these component parts.
Step 1: Parts
Top magnet ¼"dia × ¼ "long rod
Base magnet ¼"dia × ½"long rod
Safety NotesPlease do not let little children play, mouth, or risk swallowing these attractive magnets,
a serious surgical situation may result if swallowed.
Also take care to restrict access to the little button batteries which may contain mercury.
I take no responsibility for any mishap, or injury that may result or occur now or at some later time because of this project..
Step 2: LED INDICATOR
A supplier of surplus electronics and has a 5mm White LED for under $2 for you
Any white or blue LED will do.
A red led will be damaged testing the DL20xx 3 Volt lion button batteries.
Use a tweezer or a small needle nose pliers to form the flat curl on the positive Anode LED lead..