Well you need a lamp that draws some current. A typical store bought test lamp may or may not do what you want, and an LED tester will just light up bright. Something I use A LOT is an old stop / tail light socket with an 1157 bulb
You can use these (as in the above post to replace fuse) to find shorts, I used to use them to limit current flow when charging small lead batteries (bike) from an oversized charger
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You have a socket (ground)
One wire is tail (less wattage, lower current, dimmer filament)
Second wire is stop (more wattage, more current, brighter filament)
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You can wire this several ways:
A....Least wattage least current is to use the two wires to connect, leave the socket unconnected. You want to make sure it does not contact anything, IE tape it
B....Next bigger wattage, a bit more current, is to use the socket for one terminal and the tail wire for the second terminal
C....Next larger after that is to use the socket for one terminal, and the stop lamp filament for the second terminal
D....For a large load, you can use the socket for one terminal, then twist the two wires together and use both of them together for the second terminal, which of course lights both lamp filaments
