User.Identity.Name

Hello, I am working on a 4 player card game, and currently doing the hand playing routine. For debug purposes I would like to just have a button and textbox to change the player and see what that player would see. Anyways I have the button and textbox there and 4 simulated name accounts set up under the registartaion.
is there a way I can input the player name into the text box and set User.Identity.Name to be the value of the textbox? I am trying to avoid having to go through the logout, then login, then navigate back to the page that is a lot of time wasted that could be used for the actual programming.....