I'm trying to test an existing rails project with rspec. And I want to test a controller but getting an error which I can't solve :S

Here is the my spec code ;

require 'spec_helper'

describe BriefNotesController do

  before(:all) do
    @customer=Factory(:customer)
    @project=Factory(:project_started, :owner => @customer)
  end

  context 'get :new' do

    it 'should redirect to login page for not signed in users' do
      get :new, :project_id => @project.id
      response.should redirect_to("/kullanici-girisi")
    end

    it 'should be success and render new brief note page for project owner' do
      sign_in @customer
      get :new, :project_id => @project.id
      response.should be_success
    end

  end

end

Here is the my controller code ;

class BriefNotesController < ApplicationController
  before_filter :authenticate_user!
  before_filter :find_project

  def new
    @brief_note = @project.brief_notes.new
  end

  def create
    @brief_note = @project.brief_notes.build(params[:brief_note])
    if @brief_note.save
      redirect_to brief_project_path(@project)
    else
      render :action => :new
    end
  end

private
  def find_project
    @project = current_user.projects.find_by_cached_slug([params[:project_id]])
  end
end

I think current_user.projects.find_by_cached_slug method don't work. So this is the error;

Failures:

  1) BriefNotesController get :new should be success and render new brief note page for         project owner
 Failure/Error: get :new, :project_id => @project.id
 NoMethodError:
   undefined method `brief_notes' for nil:NilClass
 # ./app/controllers/brief_notes_controller.rb:6:in `new'
 # ./spec/controllers/brief_notes_controller_spec.rb:19:in `block (3 levels) in <top (required)>'