I want to use Plot with a SetDelay. Then Filling does not work. In the following, the first works, the second does not. I would like to get the second to work:
Plot[{x, 2 x}, {x, 0, 5}, Filling -> {1 -> {{2}, LightBlue}}]
test[x_] := {x, 2 x}
Plot[test[x], {x, 0, 5}, Filling -> {1 -> {{2}, LightBlue}}]