@Test void errorsOnUninstrumentedLinks() {
    List<Span> trace = List.of(
      span("a", null, "a", Kind.SERVER, "client", null, false),
      span("a", "a", "b", null, null, null, false),
      // there's no remote here, so we shouldn't see any error count
      span("a", "b", "c", Kind.CLIENT, "server", null, true),
      span("a", "b", "d", Kind.CLIENT, "server", null, true)
    );

    assertThat(new DependencyLinker().putTrace(trace).link()).containsOnly(
      DependencyLink.newBuilder().parent("client").child("server").callCount(2L).build()
    );
  }
Spans are sometimes intermediated by an unknown type of span. Prefer the nearest server when
accounting for them.
zipkin/src/test/java/zipkin2/internal/DependencyLinkerTest.java