Rails admin_only!

application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery

  def admin_only!
    if user_signed_in?
      unless current_user.admin?
        flash[:error] = "The feature you attempted to use is restricted to admins only."
        redirect_to root_url
      end
    else
      flash[:error] = "You must be signed in to use this feature."
      redirect_to root_url
    end
  end

end

application_controller_spec.rb

require 'spec_helper'

describe ApplicationController do
  include Devise::TestHelpers

  describe "#admin_only!" do
    before do
      controller.response = ActionController::TestResponse.new
    end

    context "when not logged in" do
      before do
        sign_out :user
      end

      it "redirects to the root url" do
        controller.should_receive(:redirect_to).with(root_url)
        controller.admin_only!
      end

      it "displays an appropriate error message" do
        controller.admin_only!
        flash[:error].should == "You must be signed in to use this feature."
      end
    end

    context "when logged in as non-admin user" do
      before do
        user = Factory(:user)
        sign_in user
      end

      it "redirects to the root url" do
        controller.should_receive(:redirect_to).with(root_url)
        controller.admin_only!
      end

      it "displays an appropriate error message" do
        controller.admin_only!
        flash[:error].should == "The feature you attempted to use is restricted to admins only."
      end
    end

    context "when logged in as admin user" do
      it "does not redirect" do
        user = Factory(:user, :admin => true)
        sign_in user
        controller.should_not_receive(:redirect_to)
        controller.admin_only!
      end
    end
  end
end