在QUnit测试中设置$（this）的范围

<script type=\"text/javascript\">
    APP = {};
    APP.callBack = function() {
        $(this).closest(\"input\").val(\'foobar\');
    };

    $(function() {
        $(\"#button\").click(APP.callBack);
    });
</script>
<div>
  <a id=\"button\" href=\"#\"></a>
  <input id=\"id-for-testing-only\" name=\"test\" type=\"text\" value=\"barfoo\" />
</div>

test(\"try callback with \'this\' scope\", function() {
    APP.callBack();
    equals($(\"#id-for-testing-only\").val(), \"foobar\", \"should set value to \'foobar\'\");
});