How I know my kids didn't do a damn think I told them to do

I gave my boys a list of chores to do before I got come. When I get home and starts opening the door I hear running. I walk in and the house doesn't look clean at all. I got to the kitchen and there is water on the floor and my oldest is mopping. He tries to play it off like he's been cleaning the kitchen. I tell him "You do realize you're mopping with a broom, not a mop right?" He looks down and back at me and just starts ratting out his brother and his brother hears and he starts ratting him out and then they start fighting over who didn't do what.... Teenagers...