Moq allows developers to mock protected members. I was looking for the same functionality in Rhino.Mocks but fail to find it.

Here's an example from Moq Quick Start page how to mock protected method.

// at the top of the test fixture
using Moq.Protected()

// in the test
var mock = new Mock<CommandBase>();
mock.Protected()
     .Setup<int>("Execute")
     .Returns(5);

// if you need argument matching, you MUST use ItExpr rather than It
// planning on improving this for vNext
mock.Protected()
    .Setup<string>("Execute",
        ItExpr.IsAny<string>())
    .Returns(true);

Let me know if I'm chasing something that doesn't exit.