The test does work -the takeoff config pb does just what it's meant to - amongst other things testing that the flaps are not at 0. That's satisfied by the residual 1+F. There is no requirement for the takeoff config test to be done at Flap 0 (in fact you'll get a very loud warning!) which seems to be what you're implying?
And that's why the cockpit setup procedure has for Flaps to check that the handle matches the flap indication on the ECAM. thus it can be at Flap 1.
Last edited by compressor stall; 4th May 2016 at 10:26.