title: "undefined method `env' for nil:NilClass" in 'setup_controller_for_warden' error when testing Devise using Rspec
body: <p>I'm trying to create a spec for a sign out flow by using factorygirl to create a user and then use Devise's <code>sign_in</code> method to authenticate the user, then use capybara to click the "Sign Out" link.</p>
  
  <p>I'm getting (what seems to me to be) a strange error when I run the spec:</p>
  
  <pre><code>Failures:
  
    1) Sign out flow successfully redirects to the welcome index (root)
       Failure/Error: Unable to find matching line from backtrace
       NoMethodError:
         undefined method `env' for nil:NilClass
       # /home/vagrant/.rvm/gems/ruby-2.0.0-p576/gems/devise-3.4.1/lib/devise/test_helpers.rb:24:in `setup_controller_for_warden'
  
  Finished in 0.00226 seconds (files took 3.32 seconds to load)
  1 example, 1 failure
  </code></pre>
  
  <p>Here's the spec:</p>
  
  <pre><code>require 'rails_helper'
  
  describe "Sign out flow" do
  
    include Devise::TestHelpers
  
    describe "successfully" do
      it "redirects to the welcome index (root)" do
        user = create(:user)
        sign_in user
  
  
        within '.user-info' do
          click_link 'Sign Out'
        end
  
        expect(current_path).to eq root_path
      end
    end
  end
  </code></pre>
  
  <p>And my <code>user.rb</code> factory:</p>
  
  <pre><code>FactoryGirl.define do
    factory :user do
      name "Fake User"
      sequence(:email, 100) { |n| "person#{n}@example.com" }
      password "helloworld"
      password_confirmation "helloworld"
      confirmed_at Time.now
    end
  end
  </code></pre>
  
  <p>The error seems to be triggered simply from the line <code>include Devise::TestHelpers</code>, as I've tried commenting out the entire content of the spec and still get the same error.</p>
  
  <p>I thought the Devise test helpers would work out of the box; did I miss some configuration? Thanks.</p>