title: Angular2 unit testing a switchMap
body: <p>Simple question:</p>
  
  <p>I've followed the tutorial: <a href="http://blog.thoughtram.io/angular/2016/01/06/taking-advantage-of-observables-in-angular2.html" rel="nofollow">here</a> where I have the following code:</p>
  
  <pre><code>this.term.valueChanges
    .debounceTime(400)
    .distinctUntilChanged()
    .switchMap(term =&gt; this.wikipediaService.search(term));
  </code></pre>
  
  <p>Where term is a  <a href="https://angular.io/docs/ts/latest/api/common/index/Control-class.html" rel="nofollow">Control</a> inheriting from <a href="https://angular.io/docs/ts/latest/api/common/index/AbstractControl-class.html" rel="nofollow">AbstractControl</a>, how can I trigger the valueChanges observable property, so that I can perform unit tests?</p>