I've been using a painters drop cloth from home depot, about $12 (144" x 108"). I think it is actually some form of the infamous blackout cloth (rubberized on one side). Mine had seams, of which I could get a 56 X 108 seamless section. If yours is just temporary, seams might be ok.
After you are done with the test, you can still use it as a drop cloth. I marked mine up with a sharpie pen to get the dimensions, but who cares after you spill a little paint on it.
Failure is not an option. It comes bundled with every Microsoft product