it("should NOT show preview of unsupported rgb/rgba colors", function () {
                runs(function () {
                    expectNoPreviewAtPos(25, 14);    // cursor on rgb(300, 0, 0)
                    expectNoPreviewAtPos(26, 15);    // cursor on rgb(0, 95.5, 0)
                    expectNoPreviewAtPos(27, 15);    // cursor on rgba(-0, 0, 0, 0.5)