validationEngine验证能过时不调用success函数怎么回事啊？

/ 初始化

      $(document).ready(function() {
   $("#f2").validationEngine({
       failure : function() { callFailFunction() }, 
       success : function() {changeButton() },
       });
               
      });
function changeButton() {
   alert("success!");
}
function callFailFunction() {
   alert(" fail! ");
}

<form id="f2" action="#" method="post" accept-charset="utf-8">
   <br/>
   <br/>
   <input id="some_name" type="text" name="some_name" class="text1 validate[required] text-input" value="">
    


<p><input type="submit" value="Continue &rarr;"></p>
</form>

下面这是form 表单,怎么成功了不调用success方法的？