title: what is the "expect" function used in angular js
body: <p>In the Angular documentation they write this:</p>
  
  <p><code>expect(scope.counter).toEqual(0);</code></p>
  
  <p>and this was written in many places like <a href="http://docs.angularjs.org/api/ng.%24rootScope.Scope#%24digest">here</a>. </p>
  
  <p>I just want to know what it does</p>