title: How to unit test forkJoin in Karma
body: <p>I have a code which utilizes the forkJoin it goes this way,</p>
  
  <pre><code>forkJoin(serviceRequests).subscribe((forkResults) =&gt; {
                  //Do stuff with forkResults here 
  });
  </code></pre>
  
  <p>How do I mock the subscribe so that the code inside can also be evaluated.</p>
  
  <p>I tried various things like following</p>
  
  <pre><code>spyOn(Observable, 'forkJoin').and.returnValue(of(mockedResults));
  </code></pre>