While I can't offer insight into your problem, I just wanted to chime in: These sorts of issues are why I like to use a layer on top of EF. I will usually implement a generic repository pattern.
This way, your mocks are of IRepository<T> as opposed to trying to mock up the DbSet<T>. I have successfully mocked .Include() by just populating navigation properties with fake data in the initial mock arrangement using Telerik JustMock.
This way, your mocks are of IRepository<T> as opposed to trying to mock up the DbSet<T>. I have successfully mocked .Include() by just populating navigation properties with fake data in the initial mock arrangement using Telerik JustMock.