rails admin authentication

RailsAdmin.config do |config|
  config.authorize_with do
    redirect_to main_app.root_path, error: "You are not authorized." unless current_user.is_admin?
  end
  .
  .
  .
end

--------

RSpec.describe "Rails Admin" do
  describe "authentication" do
    context "as an admin" do
      it "allows access" do
        sign_in create(:admin_user)
        visit rails_admin.dashboard_path
        expect(current_path).to eq rails_admin.dashboard_path
      end
    end
    context "as a non-admin user" do
      it "does not allow access" do
        sign_in create(:user)
        visit rails_admin.dashboard_path
        expect(current_path).to eq root_path
      end
    end
  end
end