@Override public Future<RecordMetadata> send(ProducerRecord<K, V> record) {
    return this.send(record, null);
  }
@Test void send_shouldnt_tag_binary_key() {
    MockProducer<byte[], String> mockProducer = new MockProducer<>(false, new ByteArraySerializer(), new StringSerializer());
    TracingProducer<byte[], String> tracingProducer =
      (TracingProducer<byte[], String>) kafkaTracing.producer(mockProducer);
    tracingProducer.send(new ProducerRecord<>(TEST_TOPIC, new byte[1], TEST_VALUE));
    mockProducer.completeNext();

    MutableSpan producerSpan = spans.get(0);
    assertThat(producerSpan.kind()).isEqualTo(PRODUCER);
    assertThat(producerSpan.tags())
      .containsOnly(entry("kafka.topic", TEST_TOPIC));
  }