@Test void decoderForListMessage_proto3_singleItem() {
    byte[] message = SpanBytesEncoder.PROTO3.encode(span1);
    assertThat(SpanBytesDecoderDetector.decoderForListMessage(message))
        .isEqualTo(SpanBytesDecoder.PROTO3);
  }
There is no difference between a list of size one and a single element in proto3
zipkin/src/test/java/zipkin2/SpanBytesDecoderDetectorTest.java