title: Why is my Extension Method not showing up in my test class?
body: <p>I created an extension method called <code>HasContentPermission</code> on the <code>System.Security.Principal.IIdentity</code>:</p>
  
  <pre><code>namespace System.Security.Principal
  {
      public static class IdentityExtensions
      {
          public static bool HasContentPermission
              (this IIdentity identity, int contentID)
          {
              // I do stuff here
              return result;
          }
      }
  }
  </code></pre>
  
  <p>And I call it like this:</p>
  
  <pre><code>bool hasPermission = User.Identity.HasPermission(contentID);
  </code></pre>
  
  <p>Works like a charm.  Now I want to unit test it.  To do that, all I really need to do is call the extension method directly, so:</p>
  
  <pre><code>using System.Security.Principal;
  
  namespace MyUnitTests
  {
      [TestMethod]
      public void HasContentPermission_PermissionRecordExists_ReturnsTrue()
      {
          IIdentity identity;
          bool result = identity.HasContentPermission(...
  </code></pre>
  
  <p>But <code>HasContentPermission</code> won't intellisense.  I tried creating a stub class that inherits from <code>IIdentity</code>, but that didn't work either.  Why?</p>
  
  <p>Or am I going about this the wrong way?</p>