How to mock this[]???

class TestedClass
{        
   public string this[int index]
   {
      //we are mocking the getter implementation is not important here
      get { throw new NotImplementedException(); }
   }
}

[TestFixture]
public class TestClass
{
   [Test]
   public void Test()
   {
      Mock mock = MockManager.Mock(typeof (TestedClass));
      mock.ExpectGetIndex("abc");

      TestedClass c = new TestedClass();
      Assert.AreEqual("abc", c[0]);
   }
}