Enable digest authentication at rspec controller tests

http_digest_authentication.rb

# This file goes to:
# spec/support/http_digest_authentication.rb

require 'digest/md5'
module HTTPDigestAuthentication
  def authenticate_with_http_digest(user, password, realm)
    ActionController::Base.class_eval { include ActionController::Testing }

    unless @controller.methods.include?(:real_process_with_new_base_test)
      @controller.instance_eval %q{
        alias real_process_with_new_base_test process_with_new_base_test
      }
    end

    @controller.instance_eval %Q(
      def process_with_new_base_test(request, response)
        credentials = {
          :uri => request.url,
          :realm => "#{realm}",
          :username => "#{user}",
          :nonce => ActionController::HttpAuthentication::Digest.nonce(request.env['action_dispatch.secret_token']),
          :opaque => ActionController::HttpAuthentication::Digest.opaque(request.env['action_dispatch.secret_token'])
        }
        request.env['HTTP_AUTHORIZATION'] = ActionController::HttpAuthentication::Digest.encode_credentials(request.request_method, credentials, "#{password}", false)

        real_process_with_new_base_test(request, response)
      end
    )
  end
end

spec_helper.rb

# This file goes to:
# spec/spec_helper.rb

# This file is copied to spec/ when you run 'rails generate rspec:install'
ENV["RAILS_ENV"] ||= 'test'

require File.expand_path("../../config/environment", __FILE__)
require 'rspec/rails'
require 'rspec/autorun'
# require_relative 'fast_spec_helper'
# ...

# Requires supporting ruby files with custom matchers and macros, etc,
# in spec/support/ and its subdirectories.
Dir[Rails.root.join("spec/support/**/*.rb")].each {|f| require f}

RSpec.configure do |config|
  # ...
  config.include HTTPDigestAuthentication, type: :controller
  # ...
end

xxx_controller_spec.rb

# This file goes to:
# spec/controller/api/xxx_controller_spec.rb

require 'spec_helper'

describe Api::XxxController do
  describe 'index' do
    it 'is successful' do
      authenticate_with_http_digest('name', 'password', 'realm')

      get :index, format: :json

      response.should be_success
    end

    it 'rejects the request' do
      get :index, format: :json

      response.should_not be_success
    end
  end
end