@Test void coercesZeroTimestampsToNull() {
    Span span = base.toBuilder()
      .timestamp(0L)
      .duration(0L)
      .build();

    assertThat(span.timestamp())
      .isNull();
    assertThat(span.duration())
      .isNull();
  }
Catches common error when zero is passed instead of null for a timestamp
zipkin/src/test/java/zipkin2/SpanTest.java