Problem

You would like to use factory_girl instead of the mock models described in the RSpec book (Behaviour Driven Rails – Rails Controllers – Controller specs).

Solution

Make sure that you use let! instead of let and have the following:

require 'spec_helper'

describe MessagesController do
  describe "POST create" do
    let!(:message) { Factory.create(:message) }
    
    before do 
      Message.stub(:new).and_return(message)
    end
    
    it "creates a new message" do
      Messagee.should_receive(:new).with("text" => "a quick brown fox").and_return(message)
      post :create, :message => {"text" => "a quick brown fox"}
    end
    
    it "saves the message" do
      message.should_receive(:save)
      post :create
    end

    it "redirects to the Messages index" do
      post :create
      response.should redirect_to(:action => "index")
    end
  end
end