Add a #to_json method to the serializer base

lib/active_model/serializer.rb

@@ -177,6 +177,10 @@ def json_key
       end
     end
 
+    def to_json
+      self.class.adapter.new(self).to_json
+    end
+
     def id
       object.id if object
     end

test/adapter_test.rb

@@ -38,6 +38,10 @@ def test_create_adapter_with_override
         adapter = ActiveModel::Serializer::Adapter.create(@serializer, { adapter: :json_api})
         assert_equal ActiveModel::Serializer::Adapter::JsonApi, adapter.class
       end
+
+      def test_to_json_is_sent_to_adapter
+        assert_equal JSON.parse(@serializer.to_json), {"name" => nil, "description" => nil}
+      end
     end
   end
 end