gistfile1.rb

class MoviesController < ApplicationController  
  def directors
    Movie.find_directors(params[:id])
  end
end

class Movie < ActiveRecord::Base
  # should be self.find_directors
  # should take a param
  # example:
  # def self.find_directors(movie_id)
  # end
  def find_directors
  end
end

describe MoviesController do
  describe "finding movies with the same director" do
    it 'should call the model method that returns the similar movies list' do
      Movie.should_receive(:find_directors).with("5")
      get :directors, :id => "5"
    end
  end
end
# the above passes

# VS

describe MoviesController do
  describe "finding movies with the same director" do
    it 'should call the model method that returns the similar movies list' do
      get :directors, :id => "5"
      Movie.should_receive(:find_directors).with("5")
    end
  end
end
# the above, fails

Failures:

  1) MoviesController finding movies with the same director should call the model method that returns the similar movies list
     Failure/Error: get :directors, :id => "5"
     NoMethodError:
       undefined method `find_directors' for #<Class:0x007f8b6e42b020>
     # ./app/controllers/movies_controller.rb:12:in `directors'
     # ./spec/controllers/movies_controller_spec.rb:8:in `block (3 levels) in <top (required)>'