Merge pull request rails#8066 from cfabianski/AddTestForSerialization…

…Method

Add test for code change introduced in this commit f20032f

activemodel/test/cases/serializers/json_serialization_test.rb

@@ -155,6 +155,15 @@ def @contact.favorite_quote; "Constraints are liberating"; end
     end
   end
 
+  test "as_json should keep the default order in the hash" do
+    json = @contact.as_json
+    keys = json.keys
+
+    %w(name age created_at awesome preferences).each_with_index do |field, index|
+      assert_equal keys.index(field), index
+    end
+  end
+
   test "from_json should work without a root (class attribute)" do
     json = @contact.to_json
     result = Contact.new.from_json(json)