### Question:
ListSerializer { public static <E extends DataObject> void serializeHeaderList(List<E> list, TypeKeyMaker<E> keyMaker, SerializerRegistry registry, ByteBuf outBuffer) { if (list != null) { for (E item : list) { HeaderSerializer<E> serializer = registry.getSerializer(keyMaker.make(item)); serializer.serializeHeader(item, outBuffer); } } } private  ListSerializer(); static void serializeList(List<E> list,
            TypeKeyMaker<E> keyMaker, SerializerRegistry registry, ByteBuf outBuffer); static void serializeHeaderList(List<E> list,
            TypeKeyMaker<E> keyMaker, SerializerRegistry registry, ByteBuf outBuffer);  }### Answer:
@Test public void test() { ByteBuf buffer = PooledByteBufAllocator.DEFAULT.buffer(); ListSerializer.serializeHeaderList(null, keyMaker, registry, buffer); Assert.assertEquals("Data written to buffer", 0, buffer.readableBytes()); }