controller_bootstrap.rb

$:.push File.expand_path '../../', __FILE__

module ActiveRecord
  class RecordNotFound < StandardError; end
end

require 'action_controller'
require 'app/controllers/application_controller'

module ControllerSpecHelpers

  class FakeRequest
    def parameters
      @_params ||= ActiveSupport::HashWithIndifferentAccess.new
    end
  end

  def controller
    unless @_controller
      @_controller = described_class.new
      @_controller.stub(:render)
      @_controller.stub(:redirect_to)
      @_controller.request = FakeRequest.new
    end
    @_controller
  end

  def params
    controller.params
  end

  def request
    controller.request
  end
end

RSpec.configure do |config|
  config.include ControllerSpecHelpers, :type => :controller
end

example_controller_spec.rb

require 'controller_bootstrap'
require 'app/controllers/example_controller'

describe ExampleController, :type => :controller do
  describe '#show' do
    let(:special_params) { { "key" => "values" } }

    before do
      (ServiceLayer ||= Class.new).stub(:perform_action)
      params[:special_params] = special_params
    end


    subject { controller.show }

    it 'uses the service layer with the params' do
      ServiceLayer.should_receive(:perform_action).with special_params
      subject
    end
    it "renders the template" do
      controller.should_receive(:render).with('special_example')
      subject
    end
  end
end