@Test void messagingWithoutBroker_noLinks() {
    List<Span> trace = List.of(
      span("a", null, "a", Kind.PRODUCER, "producer", null, false),
      span("a", "a", "b", Kind.CONSUMER, "consumer", null, false)
    );

    assertThat(new DependencyLinker().putTrace(trace).link())
      .isEmpty();
  }
Shows we don't assume there's a direct link between producer and consumer.
zipkin/src/test/java/zipkin2/internal/DependencyLinkerTest.java