title: How do you unit test an interface?
body: <p>For example, there is a interface <code>IMyInterface</code>, and three classes support this interface:</p>
  
  <pre><code>class A : IMyInterface
  {
  }
  
  class B : IMyInterface
  {
  }
  
  class C : IMyInterface
  {
  }
  </code></pre>
  
  <p>In the simplest way, I could write three test class : ATest, BTest, CTest and test them separately. However, since they support the same interface, most test code would be the same, it's hard to maintain. <b>How can I use a simple and easy way to test a interface that is supported by different class?</b></p>
  
  <p>(<a href="http://social.msdn.microsoft.com/forums/en-US/vststest/thread/072e5be8-2bbf-441a-a87f-c5ae5790a80c" rel="noreferrer">previously asked on the MSDN forums</a>)</p>