Fix tests for Devise's :confirmable module

The `set_confirmable_options` helper was fundamentally broken: the
code being tested is only loaded once, so simply changing values in
Spree::Auth::Config does not have any effect on the modules loaded
in Spree::User.

The only way to ensure we load the right modules is removing and
reloading the Spree::User class after stubbing the configuration.

spec/features/confirmation_spec.rb

@@ -2,9 +2,8 @@
 
 require 'spec_helper'
 
-feature 'Confirmation' do
+RSpec.feature 'Confirmation' do
   before do
-    set_confirmable_option(false)
     allow(Spree::UserMailer).to receive(:confirmation_instructions)
       .and_return(double(deliver: true))
   end
@@ -15,7 +14,7 @@
     ActionMailer::Base.default_url_options[:host] = 'http://example.com'
   end
 
-  scenario 'create a new user', :js do
+  scenario 'create a new user', js: true, confirmable: false do
     visit spree.signup_path
 
     fill_in 'Email', with: '[email protected]'

spec/models/user_spec.rb

@@ -88,16 +88,12 @@
   end
 
   describe "confirmable" do
-    it "is confirmable if the confirmable option is enabled" do
-      set_confirmable_option(true)
-      allow(Spree::UserMailer).to receive(:confirmation_instructions).and_return(double(deliver: true))
-      expect(Spree::User.devise_modules).to include(:confirmable)
-      set_confirmable_option(false)
+    it "loads Devise's :confirmable module when :confirmable is true", confirmable: true do
+      expect(Spree::User.ancestors).to include(Devise::Models::Confirmable)
     end
 
-    it "is not confirmable if the confirmable option is disabled" do
-      set_confirmable_option(false)
-      expect(Spree::User.devise_modules).to_not include(:confirmable)
+    it "does not load Devise's :confirmable module when :confirmable is false", confirmable: false do
+      expect(Spree::User.ancestors).not_to include(Devise::Models::Confirmable)
     end
   end
 end

spec/support/confirm_helpers.rb

@@ -1,17 +1,26 @@
 # frozen_string_literal: true
 
-module ConfirmHelpers
-  def set_confirmable_option(value)
-    if value
-      Spree::User.devise_modules.push(:confirmable)
-      stub_spree_preferences(Spree::Auth::Config, confirmable: true)
+RSpec.configure do |config|
+  config.around do |example|
+    if example.metadata.key?(:confirmable)
+      old_user = Spree::User
+
+      begin
+        example.run
+      ensure
+        Spree.const_set('User', old_user)
+      end
     else
-      Spree::User.devise_modules.delete(:confirmable)
-      stub_spree_preferences(Spree::Auth::Config, confirmable: false)
+      example.run
     end
   end
-end
 
-RSpec.configure do |c|
-  c.include ConfirmHelpers
+  config.before do |example|
+    if example.metadata.key?(:confirmable)
+      stub_spree_preferences(Spree::Auth::Config, confirmable: example.metadata[:confirmable])
+
+      Spree.send(:remove_const, :User)
+      load File.expand_path('../../../app/models/spree/user.rb', __FILE__)
+    end
+  end
 end