use helper instead of decorator

Probably, decorator can not successfully generate the `url`

app/helpers/application_helper.rb

@@ -24,4 +24,8 @@ def create_route_title_from_schedules(schedules, index)
     end
     route_title + '〜' + schedules[index].place.name
   end
+
+  def generate_invite_url(travel)
+    new_travel_member_url(travel_id: travel.id, key: travel.generate_invite_key)
+  end
 end

app/views/travels/_member.html.slim

@@ -5,7 +5,7 @@
   .panel-body
     | この旅行計画にメンバーを追加したい場合、以下のURLをメンバーにシェアして下さい。
     br
-    = text_field_tag(:invite_url, @travel.generate_invite_url, { readonly: true, class: 'form-control' })
+    = text_field_tag(:invite_url, generate_invite_url(@travel), { readonly: true, class: 'form-control' })
 
 br
 hr

config/environments/development.rb

@@ -39,5 +39,3 @@
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
 end
-
-Rails.application.default_url_options[:host] = 'localhost:3000'

config/environments/production.rb

@@ -74,5 +74,3 @@
   # Do not dump schema after migrations.
   config.active_record.dump_schema_after_migration = false
 end
-
-Rails.application.default_url_options[:host] = 'travel-base.herokuapp.com'

config/environments/test.rb

@@ -38,5 +38,3 @@
   # config.action_view.raise_on_missing_translations = true
   config.active_support.test_order = :random
 end
-
-Rails.application.default_url_options[:host] = 'www.example.com'

test/integration/travel_integration_test.rb

@@ -183,7 +183,9 @@ def setup
     click_link 'メンバー管理'
 
     invite_url = find('#invite_url').value
-    assert_equal travel.generate_invite_url, invite_url
+    expect_invite_url = new_travel_member_url(
+      travel_id: travel.id, key: travel.generate_invite_key)
+    assert_equal expect_invite_url, invite_url
   end
 
   test 'can add member' do
@@ -192,7 +194,9 @@ def setup
     other_user_travel = Travel.mine(twitter_user).first
 
     assert_not_includes other_user_travel.members, current_user.id
-    visit other_user_travel.generate_invite_url
+    invite_url = new_travel_member_url(
+      travel_id: other_user_travel.id, key: other_user_travel.generate_invite_key)
+    visit invite_url
     other_user_travel.reload
     assert_includes other_user_travel.members, current_user.id
   end