This may save some of youall a little headache.
I had an interesting experience when I was replacing the factory low beam bulbs with LED bulbs.
I bought the low beam LED bulbs off eBay from China.
They were guaranteed to fit my 2015 Titan.
Well, they physically fit---but did not light up when I turned them on.
So I had to go back under the wheel well liner.
I checked them with a 9-volt battery, and they would light up if I reversed the polarity of the connecting plug.
Fortunately, the plug COULD be reversed (one part of the plug turned 180 degrees from where it should be.)
But the plug had a little latching tab to keep the 2 halves of the plug from coming apart.
So my electrical wiring connectors are not latched together, but the fit was pretty tight. Hopefully it won't separate while I am driving in the dark. I guess I could have taped the halves together with electrician's tape.
Lesson learned: test the bulbs before you reinstall the fender liner.