Always, always, always test a new outlet before plugging in. Always.
I visited my sister in Colorado. She said her "friend" had wired a 50 amp outlet in the barn to plug in his RV. I looked, and sure enough there was a 50 amp outlet there. I asked about her "friend's" qualifications. He drives the RV. I took the front off the breaker box to see the wires, then followed them to the outlet, then took the outlet out to see the wires.
He had actually done a very good job. However, I KNEW it was a good job before plugging in. And I STILL tested it before plugging in!
When I ran a 50/30/20 pedestal to my home parking spot, I wired it myself, so I KNEW it was right. However, before plugging in, I STILL tested it.
Can't be too careful.
