Why does my 1 yr old lab potty in the house every few months?

I agree with Pia. I had this problem with my American Eskimo and she did the exact same thing right in front of us. It was because she was not completely potty trained and the couch provided a nice absorbent surface. We have wood floors, so that was why she chose the couch. Most dogs prefer to pee on surfaces that will absorb the urine, like grass instead of concrete.
I don't believe my dog did this to "test me" or out of spite. That's anthropomorphizing. Dogs don't know the difference between right and wrong. They only know that if they do this action, that such and such results. Therefore, if you react negatively and punish the dog for urinating in the house; it won't teach her that it's wrong. It will only teach her that you will react negatively when she does that.

Some times dogs just like to test you, even if they know what they are doing is wrong. I know my pup goes to the bathroom on the floor if i leave him by himself, even if i'm just outside for two minutes.

Well, actually, she is not housetrained if she is still have accidents. Have you recently gotten a new pet? She could be marking her territory. I would stay on top of her and watch her like a hawk, making sure she is put on a regular schedule since she is still having accidents.