@Test public void doesNotStackOverflowOnToString() {

  Span span = tracing.tracer().newTrace();
  SpanCustomizerShield shield = new SpanCustomizerShield(span);
  assertThat(shield.toString())
    .isNotEmpty()
    .isEqualTo("SpanCustomizer(RealSpan(" + span.context().traceIdString() + "/" + span.context()
      .spanIdString() + "))");
}