diff --git a/config/routes.rb b/config/routes.rb
index ca9d77590..eada47681 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -312,7 +312,7 @@ RedmineApp::Application.routes.draw do
 
   resources :auth_sources do
     member do
-      get 'test_connection'
+      get 'test_connection', :as => 'try_connection'
     end
   end
 
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 91e0d8cc6..5c166687e 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -492,3 +492,14 @@ end
 # Simple module to "namespace" all of the API tests
 module ApiTest
 end
+
+# URL helpers do not work with config.threadsafe!
+# https://github.com/rspec/rspec-rails/issues/476#issuecomment-4705454
+ActionView::TestCase::TestController.instance_eval do
+  helper Rails.application.routes.url_helpers
+end
+ActionView::TestCase::TestController.class_eval do
+  def _routes
+    Rails.application.routes
+  end
+end
diff --git a/test/unit/helpers/application_helper_test.rb b/test/unit/helpers/application_helper_test.rb
index d44dba8a2..40a85473e 100644
--- a/test/unit/helpers/application_helper_test.rb
+++ b/test/unit/helpers/application_helper_test.rb
@@ -21,6 +21,7 @@ require File.expand_path('../../../test_helper', __FILE__)
 
 class ApplicationHelperTest < ActionView::TestCase
   include ERB::Util
+  include Rails.application.routes.url_helpers
 
   fixtures :projects, :roles, :enabled_modules, :users,
            :repositories, :changesets,
diff --git a/test/unit/lib/redmine/helpers/gantt_test.rb b/test/unit/lib/redmine/helpers/gantt_test.rb
index 819b506e3..291662d67 100644
--- a/test/unit/lib/redmine/helpers/gantt_test.rb
+++ b/test/unit/lib/redmine/helpers/gantt_test.rb
@@ -34,6 +34,7 @@ class Redmine::Helpers::GanttHelperTest < ActionView::TestCase
   include ProjectsHelper
   include IssuesHelper
   include ERB::Util
+  include Rails.application.routes.url_helpers
 
   def setup
     setup_with_controller