void assertPostSpansV1Success(List<Span> spans) throws IOException {
    try (Response response = postSpansV1(spans)) {
      assertThat(response.code()).isEqualTo(202);
    }
  }
Normally, a span can be reported twice: for client and server. However, there are bugs that
happened where several updates went to the same span id. {@link ZipkinExtension#collectorMetrics}
can be used to help ensure a span isn't reported more times than expected.
zipkin-junit5/src/test/java/zipkin2/junit5/ZipkinExtensionTest.java