@Test void traceByServiceSpan_emptyWhenNoEndpoints() {
    Span span = spanWithoutAnnotationsOrTags.toBuilder().localEndpoint(null).build();

    assertThat(consumer.accept(List.of(span)))
      .isInstanceOf(ResultSetFutureCall.class);
  }
To allow lookups w/o a span name, we index "". "" is used instead of null to avoid creating
tombstones.
zipkin-storage/cassandra/src/test/java/zipkin2/storage/cassandra/CassandraSpanConsumerTest.java