单元测试DOM元素外部指令

Question

如何在指令外测试DOM元素，例如根据输入添加和删除“活动”类到选项卡。帮我写一下angular.element（'。active'）的单元测试用例.removeClass（'active'）;

<div ng-controller="myCtrl">
<div id="tabs">
<div id="tab1" class="active" tab-navigation>Tab 1</div>
<div id="tab2" tab-navigation>Tab 2</div>
<div id="tab3" tab-navigation>Tab 3</div>
</div>
<div class="active" id="tab">  
<input type="text" ng-model=inputvalue" my-directive/>
<button value="submit"/>
</div>
</div>

app.directive('myDirective',function(){
return{
require:'ngModel',
link:function(scope,element,attr,ngModelCtrl){
ngModelCtrl.$parsers.unshift(function(inputValue)
{
 if(inputValue==='') {
 angular.element('.active').removeClass('active');
}    
};
});