@Test public void localRootId_joinSpan_notYetSampled() {

  TraceContext context1 = TraceContext.newBuilder().traceId(1).spanId(2).build();
  TraceContext context2 = TraceContext.newBuilder().traceId(1).spanId(3).build();
  localRootId(context1, context2, ctx -> tracer.joinSpan(ctx.context()));
}