@Test void enqueue_finish() {
    Call<List<DependencyLink>> call = new AggregateDependencyLinks(List.of(
      Call.create(List.of(DependencyLink.newBuilder().parent("a").child("b").callCount(1).build())),
      Call.create(List.of(DependencyLink.newBuilder().parent("a").child("b").callCount(3).build()))
    ));

    Callback<List<DependencyLink>> callback = mock(Callback.class);

    call.enqueue(callback);

    verify(callback)
      .onSuccess(List.of(DependencyLink.newBuilder().parent("a").child("b").callCount(4).build()));
  }
This shows that regardless of success or error, we block on completion
zipkin/src/test/java/zipkin2/internal/AggregateCallTest.java