static <T> T parse(JsonSerializers.ObjectParser<T> parser, String json) {
    try {
      JsonParser jsonParser = JsonSerializers.JSON_FACTORY.createParser(json);
      jsonParser.nextToken();
      return parser.parse(jsonParser);
    } catch (IOException e) {
      throw new UncheckedIOException(e);
    }
  }
This isn't a test of what we "should" accept as a span, rather that characters that trip-up
json don't fail in SPAN_PARSER.
zipkin-storage/elasticsearch/src/test/java/zipkin2/elasticsearch/JsonSerializersTest.java