Update fragment cache to support namespaced objects

test/adapter/fragment_cache_test.rb

@@ -4,11 +4,14 @@ module ActiveModel
     class Adapter
       class FragmentCacheTest < Minitest::Test
         def setup
+          @spam            = Spam::UnrelatedLink.new(id: "spam-id-1")
           @author          = Author.new(name: 'Joao M. D. Moura')
           @role            = Role.new(name: 'Great Author', description:nil)
           @role.author     = [@author]
           @role_serializer = RoleSerializer.new(@role)
+          @spam_serializer = Spam::UnrelatedLinkSerializer.new(@spam)
           @role_hash       = FragmentCache.new(RoleSerializer.adapter.new(@role_serializer), @role_serializer, {})
+          @spam_hash       = FragmentCache.new(Spam::UnrelatedLinkSerializer.adapter.new(@spam_serializer), @spam_serializer, {})
         end
 
         def test_fragment_fetch_with_virtual_attributes
@@ -20,6 +23,13 @@ module ActiveModel
           }
           assert_equal(@role_hash.fetch, expected_result)
         end
+
+        def test_fragment_fetch_with_namespaced_object
+          expected_result = {
+            id: @spam.id
+          }
+          assert_equal(@spam_hash.fetch, expected_result)
+        end
       end
     end
   end