public abstract byte[] encode(MutableSpan input);
@Test void localSpan_JSON_V2() {
    assertThat(new String(encoder.encode(localSpan), UTF_8))
        .isEqualTo(
            "{\"traceId\":\"dc955a1d4768875d\",\"id\":\"dc955a1d4768875d\",\"name\":\"encode\",\"timestamp\":1510256710021866,\"duration\":1117,\"localEndpoint\":{\"serviceName\":\"isao01\",\"ipv4\":\"10.23.14.72\"}}");
  }