title: angular ng-class does not react on click
body: <p>I am trying to use ng-class and bind a class to an expression so, that I can unit test the expression binding. But, it seems that I am missing something.</p>
  <p>The button:</p>
  <pre><code>&lt;li&gt;&lt;a class=&quot;&quot;  ng-click=&quot;onAddInterface()&quot;&gt;&lt;i class=&quot;icon-plus-sign&quot;&gt;&lt;/i&gt; add interface &lt;/a&gt;&lt;/li&gt;
  </code></pre>
  <p>The panel that should collapse and expand:</p>
  <pre><code>&lt;div class=&quot;collapse&quot; ng-class=&quot;{in:showCreateNewInterfacePanel}&quot;&gt;&lt;div&gt; 
  </code></pre>
  <p>the function that is fired</p>
  <pre><code>$scope.onAddInterface=function(){
    $scope.showCreateNewInterfacePanel=true;
  }
  </code></pre>
  <p>anyway clicking the link nothing happens.</p>
  <p>Am I missing something?</p>