I found a great example from this SO question which demonstrates how to fake future instances of objects. Here's an example from that question:
[TestClass]
public class UnitTest1
{
[TestMethod]
public void TestMethod1()
{
ClassLibrary1.Child myChild = new ClassLibrary1.Child();
using (ShimsContext.Create())
{
ClassLibrary1.Fakes.ShimChild.AllInstances.addressGet = (instance) => "foo";
ClassLibrary1.Fakes.ShimParent.AllInstances.NameGet = (instance) => "bar";
Assert.AreEqual("foo", myChild.address);
Assert.AreEqual("bar", myChild.Name);
}
}
}
This looks like it will do the trick for me.