Set timestamps after clearing changes

Rather than redefining #created_at and #updated_at, we can use the
existing methods and just set them if there aren't already values
present. We need to do this after clearing changes information,
otherwise the times end up getting converted to the wrong zone.

lib/factory_bot/strategy/stub.rb

@@ -32,6 +32,7 @@ module FactoryBot
         evaluation.object.tap do |instance|
           stub_database_interaction_on_result(instance)
           clear_changes_information(instance)
+          set_timestamps(instance)
           evaluation.notify(:after_stub, instance)
         end
       end
@@ -64,35 +65,6 @@ module FactoryBot
             end
           end
         end
-
-        created_at_missing_default = result_instance.respond_to?(:created_at) && !result_instance.created_at
-
-        if created_at_missing_default
-          result_instance.instance_eval do
-            def created_at
-              @created_at ||= Time.now.in_time_zone
-            end
-
-            def created_at=(date)
-              @created_at = date
-            end
-          end
-        end
-
-        has_updated_at = result_instance.respond_to?(:updated_at)
-        updated_at_no_default = has_updated_at && !result_instance.updated_at
-
-        if updated_at_no_default
-          result_instance.instance_eval do
-            def updated_at
-              @updated_at ||= Time.current
-            end
-
-            def updated_at=(date)
-              @updated_at = date
-            end
-          end
-        end
       end
 
       def clear_changes_information(result_instance)
@@ -100,6 +72,28 @@ module FactoryBot
           result_instance.clear_changes_information
         end
       end
+
+      def set_timestamps(result_instance)
+        if missing_created_at?(result_instance)
+          result_instance.created_at = Time.current
+        end
+
+        if missing_updated_at?(result_instance)
+          result_instance.updated_at = Time.current
+        end
+      end
+
+      def missing_created_at?(result_instance)
+        result_instance.respond_to?(:created_at) &&
+          result_instance.respond_to?(:created_at=) &&
+          result_instance.created_at.blank?
+      end
+
+      def missing_updated_at?(result_instance)
+        result_instance.respond_to?(:updated_at) &&
+          result_instance.respond_to?(:updated_at=) &&
+          result_instance.updated_at.blank?
+      end
     end
   end
 end