Add test for calling a url helper in Mapper#direct

actionpack/test/dispatch/routing/custom_url_helpers_test.rb

@@ -32,6 +32,7 @@ class Product < Linkable; end
 
     direct(:website)  { "http://www.rubyonrails.org" }
     direct("string")  { "http://www.rubyonrails.org" }
+    direct(:helper)   { basket_url }
     direct(:linkable) { |linkable| [:"#{linkable.linkable_type}", { id: linkable.id }] }
     direct(:params)   { |params| params }
     direct(:symbol)   { :basket }
@@ -65,6 +66,9 @@ def test_direct_paths
     assert_equal "http://www.rubyonrails.org", string_path
     assert_equal "http://www.rubyonrails.org", Routes.url_helpers.string_path
 
+    assert_equal "http://www.example.com/basket", helper_url
+    assert_equal "http://www.example.com/basket", Routes.url_helpers.helper_url
+
     assert_equal "/categories/1", linkable_path(@category)
     assert_equal "/categories/1", Routes.url_helpers.linkable_path(@category)
     assert_equal "/collections/2", linkable_path(@collection)
@@ -99,6 +103,9 @@ def test_direct_urls
     assert_equal "http://www.rubyonrails.org", string_url
     assert_equal "http://www.rubyonrails.org", Routes.url_helpers.string_url
 
+    assert_equal "http://www.example.com/basket", helper_url
+    assert_equal "http://www.example.com/basket", Routes.url_helpers.helper_url
+
     assert_equal "http://www.example.com/categories/1", linkable_url(@category)
     assert_equal "http://www.example.com/categories/1", Routes.url_helpers.linkable_url(@category)
     assert_equal "http://www.example.com/collections/2", linkable_url(@collection)