SpanNode buildTree(List<Span> trace) {
    // TRACE is sorted with root span first, lets reverse them to make
    // sure the trace is stitched together by id.
    List<Span> copy = new ArrayList<>(trace);
    Collections.reverse(copy);

    return new SpanNode.Builder(logger).build(copy);
  }
Same as {@link #constructsTraceTree()}, except with shared span ID
zipkin/src/test/java/zipkin2/internal/SpanNodeTest.java