@Test
public void testOldImage() throws IOException {

  String input = String.format(RECORD_FORMAT,
      "\"OldImage\":{" +
      "  \"Message\":{" +
      "    \"S\":\"New item!\"" +
      "  }," +
      "  \"Id\":{" +
      "    \"N\":\"101\"" +
      "  }" +
      "}");
  DynamodbEvent event = DynamodbEventDeserializer.deserialize(input);
  String result = new DynamodbEventSerializer().serialize(event.getRecords().get(0));
  String expected = String.format(EXPECTED_FORMAT, "\"oldImage\":{\"Message\":\"New item!\",\"Id\":101}");
  assertEquals(expected, result);
}