public abstract long nextTraceIdHigh();
@Test void randomLong_epochSecondsPlusRandom() {
    Platform platform = new Platform.Jre7() {
      @Override public long currentTimeMicroseconds() {
        return 1465510280000000L; // Thursday, June 9, 2016 10:11:20 PM
      }
    };

    long traceIdHigh = platform.nextTraceIdHigh();

    assertThat(HexCodec.toLowerHex(traceIdHigh)).startsWith("5759e988");
  }