// Arrange

   var mock = MockRepository.GenerateMock<IMyInterface>();

   mock.Expect( m => m.Method() ).Return( value ).Repeat.AtLeastOnce();

   //  Act

   var testClass = new TestClass( mock ); // injection of mocked object

   var expected = ...expected result from method...
   var actual = testClass.TestMethod();

   // Assert

   Assert.AreEqual( expected, actual );

   mock.VerifyAllExpectations();