@Test protected void getTraces_groupsTracesTogether(TestInfo testInfo) throws Exception {
    String testSuffix = testSuffix(testInfo);
    Span traceASpan1 = spanBuilder(testSuffix).timestamp((TODAY + 1) * 1000L).build();
    Span traceASpan2 = traceASpan1.toBuilder().id("2").timestamp((TODAY + 2) * 1000L).build();

    String traceId2 = newTraceId();
    Span traceBSpan1 = traceASpan1.toBuilder().traceId(traceId2).build();
    Span traceBSpan2 = traceASpan2.toBuilder().traceId(traceId2).build();

    accept(traceASpan1, traceBSpan1, traceASpan2, traceBSpan2);

    assertGetTracesReturns(
      requestBuilder().build(),
      List.of(traceASpan1, traceASpan2), List.of(traceBSpan1, traceBSpan2)
    );
  }
This is unlikely and means instrumentation sends empty spans by mistake.
zipkin-tests/src/main/java/zipkin2/storage/ITSpanStore.java