I plan to mount floodlights on the back of my house. I have a Romex running through the wall between the mounting point and my electrical box. I want to test my floodlight before I go to the effort of getting on a ladder and installing it - I want to make sure it is bright enough and dims appropriately. Next to my back door (my testing location) I have a normal 1-gang, 2 socket outlet.
The floodlight itself is dumb. Just a bulb socket and the neutral/load/ground wires. I very easily took an extension cord, cut it in half*, plugged it into the outlet, and wired the other end to the floodlight. Viola - easily test the floodlight, it lights up, it's bright.
Now I want to test the Smart Dimmer in the circuit, to make sure it dims the way I want it to. The smart dimmer requires a neutral wire. The way I am thinking about this is along the lines of "I just need to get power to this wire..." and I have this second outlet so... Can I just cut another extension cord in half, plug it into the second outlet and wire one of the wires to the smart switch's neutral wire? If so, which of the two wires would I use, and how would I determine which one to use with a multimeter (to be absolutely certain the outlet isn't wired backwards or something)?
* I didn't actually do this, I had a plug I cut off something I was throwing away but I figured this description was more complicated than it needed to be.