title: is it possible to mock/fake an extension method?
body: <p>I'm using a controller extension, and I tried to mock it using FakeItEasy (v 1.7.4) like this:</p>
  
  <pre><code>A.CallTo(() =&gt; controller.RenderView(A&lt;string&gt;.Ignored,A&lt;object&gt;.Ignored,null)).Returns("");
  </code></pre>
  
  <p>but I get this error:</p>
  
  <pre><code>System.NullReferenceException : Object reference not set to an instance of an object.
  at System.Object.GetType()
  at FakeItEasy.Creation.ProxyGeneratorSelector.MethodCanBeInterceptedOnInstance(MethodInfo method, Object callTarget, ref String failReason)
  at FakeItEasy.Configuration.DefaultInterceptionAsserter.AssertThatMethodCanBeInterceptedOnInstance(MethodInfo method, Object callTarget)
  at FakeItEasy.Configuration.FakeConfigurationManager.CallTo(Expression`1 callSpecification)
  </code></pre>