@Test void messageWithSingleThriftSpan() throws Exception {
    KafkaCollector.Builder builder = builder("single_span");

    byte[] bytes = THRIFT.encode(CLIENT_SPAN);
    produceSpans(bytes, builder.topic);

    try (KafkaCollector collector = builder.build()) {
      collector.start();
      assertThat(receivedSpans.take()).containsExactly(CLIENT_SPAN);
    }

    assertThat(kafkaMetrics.messages()).isEqualTo(1);
    assertThat(kafkaMetrics.messagesDropped()).isZero();
    assertThat(kafkaMetrics.bytes()).isEqualTo(bytes.length);
    assertThat(kafkaMetrics.spans()).isEqualTo(1);
    assertThat(kafkaMetrics.spansDropped()).isZero();
  }
Ensures legacy encoding works: a single TBinaryProtocol encoded span
zipkin-collector/kafka/src/test/java/zipkin2/collector/kafka/ITKafkaCollector.java