trying to SimpleDelegator an AREL object

example.rb

# based on http://tatey.com/2012/02/07/mocking-with-minitest-mock-and-simple-delegator/

class Order < ActiveRecord::Base
  # …
end

class MyController < ApplicationController
  def index
    @orders = Order.find(:all)
  end
end


# mocha version of a controller test involving AREL:
  test "it should display an index page with all orders" do
    ::Order.expects(:find).with(:all).returns([])

    get :index

    assert_template :index
    assert_response :success
  end

# Simple Delegator version?
  test "it should display an index page with blocks" do
    mock_block = Class.new SimpleDelegator do
      def find(...)
        []
      end
    end

    # this is where I'm stuck.  How can I rig the controller context so that it uses mock_block instead of the default Order.find
    # controller.order = mock_order.new(Order.new)

    get :index

    assert_template :index
    assert_response :success
  end