How can I improve the isolation for this controller spec? So I'm doing things the BDD way, writing features first, then moving on to writing specs to add more detail to the mix as I move down the layers.

One thing that bothered me, but isn't a big problem, is that when I got to the controller part of the stack, I have calls to the User and Todo model in my controller spec.

Is this okay and normal? Or should I be stubbing these things out?

describe TodosController do
  let(:user) { Factory(:user) }

  describe "post 'create'" do
    lambda {
      post :create
    }.should change(user.todos, :count).by(1)
  end 
end
It's fine to test how controllers alter models.