Mocking on Rails

Gregory Moeck's awesome post Stubbing is Not Enough got my brain back on the subject of mocking. Readers of this blog may note that I had quite a rant against mocking almost a year ago and Gregory posted a response. I think the result of that post and the discussion that ensued was not that mocking and/or stubbing were bad practices, but that when they are applied inappropriately they can quickly deteriorate the tests and the design of an application.

After reading Gregory's article, I wanted to revisit the state of mocking in Rails applications. One of the things I noticed in his article was that he was addressing some ruby classes and their interactions. He enforced the OO concepts of message passing and how mocks are better than stubs at testing very OO code. While I really like his solution, something was nagging at me: how can I do this in Rails?

For example, here is the stock rails scaffold controller and functional test:

class PostsController < ApplicationController
  # GET /posts
  # GET /posts.json
  def index
    @posts = Post.all

    respond_to do |format|
      format.html # index.html.erb
      format.json { render :json => @posts }
    end
  end
end

class PostsControllerTest < ActionController::TestCase
  setup do
    @post = posts(:one)
  end

  test "should get index" do
    get :index
    assert_response :success
    assert_not_nil assigns(:posts)
  end
end

What can I mock? In Gregory Moeck's example, the ticket reservation object was passed in to the ticket machine interface (dependency injection) so we could easily mock the ticket reservation role and assert that the ticket machine interface interacted with it properly. He also intentionally doesn't touch the @current_display variable because it is internal to the system.

In our Rails controller and functional test, we can observe the following:

1. The actions taken by the controller are internal, not based on roles it should interact with
2. The functional test is testing internal state (assigns) and not messages passed by the controller

My gut at this point says I'm on an integration boundary between the user and my internal system. So that means I would have an integration test on the controller. But still, the signature of a rails controller to call activerecord and render doesn't seem to lend itself to encapsulation and mocking.

At this point I attempted to write what I thought was a change to the way controllers work using dependency injection and object composition, but I failed at it. So I'm leaving this post with some open questions:

1. What is the proper way to test rails requests with mocking?
2. What is the proper way to do an integration test, and how deep should it go (i.e. beyond the point that you have covered with unit tests)?
3. Are there other web frameworks out there with great encapsulation as a best-practice?

Super extra bonus points if you post links to open source projects that have a test suite that actually do these things well. Thanks.