@Test void errorsOnInstrumentedLinks() {
    List<Span> trace = List.of(
      span("a", null, "a", Kind.SERVER, "foo", null, false),
      span("a", "a", "b", null, null, null, false),
      span("a", "b", "c", Kind.CLIENT, "bar", "baz", true),
      span("a", "b", "d", Kind.CLIENT, "bar", "baz", false)
    );

    assertThat(new DependencyLinker().putTrace(trace).link()).containsOnly(
      DependencyLink.newBuilder().parent("foo").child("bar").callCount(2L).build(),
      DependencyLink.newBuilder().parent("bar").child("baz").callCount(2L).errorCount(1L).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