title: Testing AdMob on iOS
body: <p>Beginning using <code>AdMob</code> in an iOS app, I have this question:</p>
  
  <p>When I am testing my app, I should not be using real adds. For that I use:</p>
  
  <pre><code>bannerUnitID = "ca-app-pub-3940256099942544/2934735716" // Provided in Googl’s tutorial.
  </code></pre>
  
  <p>All is fine with that. But I read I can also add my device for test using this:</p>
  
  <pre><code>// Requests test ads on test devices. 
  request.testDevices = ["2077ef9a63d2b398840261c8221a0c9b"] // Using the proper code for my device obviously.
  </code></pre>
  
  <p>What is the difference between using the first way and the second way?</p>
  
  <p>I tried and could see that with the second way, I seem to be getting real adds.
  It is not clear to me, what is going on here. Anyone with a clear view? Please explain.</p>