@Test void constructsTraceTree_sharedId() {
    List<Span> trace = List.of(
      Span.newBuilder().traceId("a").id("a").build(),
      Span.newBuilder().traceId("a").parentId("a").id("b").build(),
      Span.newBuilder().traceId("a").parentId("a").id("b").shared(true).build(),
      Span.newBuilder().traceId("a").parentId("b").id("c").build()
    );
    assertAncestry(trace);
  }
Same as {@link #constructsTraceTree()}, except with shared span ID
zipkin/src/test/java/zipkin2/internal/SpanNodeTest.java