Devise, undefined local variable or method current_user
===

I have `Project` controller and rspec file for it. I'm usig `current_user` helper in this way:


    # projects_controller_spec.rb

    describe "user signed in" do
      before(:each) { sign_in @user }
      after(:each)  { sign_out @user}
    
      describe "GET index" do      
        it "assigns all projects as @projects" do
          project = FactoryGirl.create(:project, :user => current_user)
          get :index, {}, valid_session
          assigns(:projects).should eq([project])
        end
      end
      ...
    end

The helpers `sign_in` and `sign_out` seem to work fine but I'v got an error on `current_user`:

    undefined local variable or method `current_user'

What might be a problem, how to fix it?