function createMockElement() {
        return $("<div/>")
            .css({
                position: "absolute",
                left: "-10000px",
                top: "-10000px"
            })
            .appendTo($("body"));
    }
Returns a mock element (in the test runner window) that's offscreen, for
parenting UI you want to unit-test. When done, make sure to delete it with
remove().
@return {jQueryObject} a jQuery object for an offscreen div