Rails: how to write an anonymous spec controller to test authorisation - ruby-on-rails

Question

I have a controller, AdminController, which sets the various authorisation levels for the rest of the CMS. Because there are no controller actions, just methods, I began to research ways to test these against controllers.
The conclusion I came to was that they needed to be tested independently of the controllers they are used in (I want to to steer clear of integration testing if possible, like capybara etc).
I found some articles like this one to help me along.
So far I have written this spec which is failing with the errors below. I am not sure about it to be honest and wanted to here what SO community had to say on what I am trying to achieve.
describe AdminController do
controller do
before_filter :authorize_fixture_uploader!
def index
render text: 'Hello World'
end
end
let(:admin){FactoryGirl.create(:admin)}
describe "authentication" do
before do
sign_in admin
allow(controller).to receive(:current_admin).and_return(admin)
end
describe "authorize_fixture_uploader! helper" do
context "signed in" do
before do
allow(:admin).to receive(:authorize_fixture_uploader!).and_return(false)
get :index
end
it "redirects do admin_home_path" do
expect(response).to redirect_to admin_home_path
end
end
end
end
end
and here is the controller
class AdminController < ApplicationController
before_filter :authenticate_admin!
def authorize_fixture_uploader!
unless current_admin.fixture_uploader?
return redirect_to(admin_home_path)
end
end
end
This test is giving me the error
1) AdminController authentication authorize_fixture_uploader! helper signed in redirects do admin_home_path
Failure/Error: allow(:admin).to receive(:authorize_fixture_uploader?).and_return(false)
TypeError:
can't define singleton
I am worried its because my whole approach to this is wrong. Help would most certainly be appreciated.
Updated thanks to #blelump's answer.
I had a type which was causing the first issue. But Now I am getting error
undefined method `authorize_fixture_uploader?' for #<RSpec::Core::ExampleGroup::Nested_1::Nested_1::Nested_1::Nested_1:0x007f9357857108>
The logic behind this i throwing me a bit. How am I to test these methods independent of the controllers they are used?

Answer 1

You have a typo:
allow(:admin).to receive(:authorize_fixture_uploader!).and_return(false)
Now you're trying to add authorize_fixture_uploader! to Symbol. Just start with controller variable:
allow(controller).to receive(:authorize_fixture_uploader!).and_return(false)

Answer 2

Aside from the poor attention detail highlight by blelump above, the real flaw in my approach was the lack of routes. I found a very useful article from pivotal labs http://pivotallabs.com/adding-routes-for-tests-specs-with-rails-3/ which saved the day.
Read the article, but it essentially boils down to this.
require 'spec_helper'
class InheritsFromAdminController < AdminController
def show
render :text => "foo"
end
end
describe InheritsFromAdminController do
before do
Rails.application.routes.draw do
# add the route that you need in order to test
match '/foo' => "inherits_from_admin#show"
# re-drawing routes means that you lose any routes you defined in routes.rb
# so you have to add those back here if your controller references them
match '/login' => "sessions/new", :as => login
end
end
after do
# be sure to reload routes after the tests run, otherwise all your
# other controller specs will fail
Rails.application.reload_routes!
end
it "requires logged-in users" do
get :show
response.should redirect_to("/login")
end
end