Rails test to reproduce https://github.com/rails/rails/issues/14411

test.diff

diff --git a/activerecord/test/cases/adapters/postgresql/hstore_test.rb b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
index 90ec152..640ca73 100644
--- a/activerecord/test/cases/adapters/postgresql/hstore_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
@@ -258,6 +258,34 @@ class PostgresqlHstoreTest < ActiveRecord::TestCase
       Hstore.update_all tags: { }
       assert_equal({ }, hstore.reload.tags)
     end
+
+    class TagCollection
+      def initialize(hash); @hash = hash end
+      def to_hash; @hash end
+      def self.load(hash); new(hash) end
+      def self.dump(object); object.to_hash end
+    end
+
+    class HstoreWithSerialize < Hstore
+      serialize :tags, TagCollection
+    end
+
+    def test_hstore_with_serialized_attributes
+      HstoreWithSerialize.create! tags: TagCollection.new({"one" => "two"})
+      record = HstoreWithSerialize.first
+      assert_instance_of TagCollection, record.tags
+      assert_equal({"one" => "two"}, record.tags.to_hash)
+      record.tags = TagCollection.new("three" => "four")
+      record.save!
+      assert_equal({"three" => "four"}, HstoreWithSerialize.first.tags.to_hash)
+    end
+
+    def test_clone_hstore_with_serialized_attributes
+      HstoreWithSerialize.create! tags: TagCollection.new({"one" => "two"})
+      record = HstoreWithSerialize.first
+      dupe = record.dup
+      assert_equal({"one" => "two"}, dupe.tags.to_hash)
+    end
   end
 
   private