### Question:
HealthCheckerFactory { public static String serialize(AbstractHealthChecker healthChecker) { try { return MAPPER.writeValueAsString(healthChecker); } catch (JsonProcessingException e) { throw new NacosSerializationException(healthChecker.getClass(), e); } }  static void registerSubType(AbstractHealthChecker extendHealthChecker); static void registerSubType(Class<? extends AbstractHealthChecker> extendHealthCheckerClass,
            String typeName); static None createNoneHealthChecker(); static AbstractHealthChecker deserialize(String jsonString); static String serialize(AbstractHealthChecker healthChecker);  }### Answer:
@Test public void testSerialize() { Tcp tcp = new Tcp(); String actual = HealthCheckerFactory.serialize(tcp); assertTrue(actual.contains("\"type\":\"TCP\"")); }