With the Artboard tool the active artboard's name was drawn twice: by the canvas, as for every artboard, and by the tool, a little higher. The test draws a frame with two artboards and checks that each name is painted once and that the active artboard's sits where the other's does. It fails without the canvas skipping the tool-labelled artboard (two labels for the active one) and without the tool's label position (8 points to the right and 11 higher than the other name).