assertStatsApproxEqual(OTHER_ONE_VALUE_STATS, oneValueAccumulator.yStats());
    assertStatsApproxEqual(
        OTHER_ONE_VALUE_STATS, oneValueAccumulatorByAddAllEmptyPairedStats.yStats());
    assertStatsApproxEqual(OTHER_TWO_VALUES_STATS, twoValuesAccumulator.yStats());
    assertStatsApproxEqual(
        OTHER_TWO_VALUES_STATS, twoValuesAccumulatorByAddAllPartitionedPairedStats.yStats());

   *
   * <ul>
   *   <li>Both {@code xStats} and {@code yStats} must have the same {@code count}.
   *   <li>If that {@code count} is 1, {@code sumOfProductsOfDeltas} must be exactly 0.0.
   *   <li>If that {@code count} is more than 1, {@code sumOfProductsOfDeltas} must be finite.
   * </ul>
   */
  PairedStats(Stats xStats, Stats yStats, double sumOfProductsOfDeltas) {
    this.xStats = xStats;
    this.yStats = yStats;

              + (values.xStats().mean() - xStats.mean())
                  * (values.yStats().mean() - yStats.mean())
                  * values.count();
    }
    yStats.addAll(values.yStats());
  }

  /** Returns an immutable snapshot of the current statistics. */
  public PairedStats snapshot() {
    return new PairedStats(xStats.snapshot(), yStats.snapshot(), sumOfProductsOfDeltas);
  }

    assertStatsApproxEqual(OTHER_ONE_VALUE_STATS, oneValueAccumulator.yStats());
    assertStatsApproxEqual(
        OTHER_ONE_VALUE_STATS, oneValueAccumulatorByAddAllEmptyPairedStats.yStats());
    assertStatsApproxEqual(OTHER_TWO_VALUES_STATS, twoValuesAccumulator.yStats());
    assertStatsApproxEqual(
        OTHER_TWO_VALUES_STATS, twoValuesAccumulatorByAddAllPartitionedPairedStats.yStats());

    assertThat(EMPTY_PAIRED_STATS.toString())
        .isEqualTo("PairedStats{xStats=Stats{count=0}, yStats=Stats{count=0}}");
    assertThat(MANY_VALUES_PAIRED_STATS.toString())
        .isEqualTo(
            "PairedStats{xStats="
                + MANY_VALUES_PAIRED_STATS.xStats()
                + ", yStats="
                + MANY_VALUES_PAIRED_STATS.yStats()
                + ", populationCovariance="

    assertThat(EMPTY_PAIRED_STATS.toString())
        .isEqualTo("PairedStats{xStats=Stats{count=0}, yStats=Stats{count=0}}");
    assertThat(MANY_VALUES_PAIRED_STATS.toString())
        .isEqualTo(
            "PairedStats{xStats="
                + MANY_VALUES_PAIRED_STATS.xStats()
                + ", yStats="
                + MANY_VALUES_PAIRED_STATS.yStats()
                + ", populationCovariance="

   * versions.
   */
  public static Stats fromByteArray(byte[] byteArray) {
    checkNotNull(byteArray);
    checkArgument(
        byteArray.length == BYTES,
        "Expected Stats.BYTES = %s remaining , got %s",
        BYTES,
        byteArray.length);
    return readFrom(ByteBuffer.wrap(byteArray).order(ByteOrder.LITTLE_ENDIAN));
  }

  /**

    stats = cache.stats();
    assertThat(stats.requestCount()).isEqualTo(3);
    assertThat(stats.hitCount()).isEqualTo(1);
    assertThat(stats.hitRate()).isEqualTo(1.0 / 3);
    assertThat(stats.missCount()).isEqualTo(2);
    assertThat(stats.missRate()).isEqualTo(2.0 / 3);
    assertThat(stats.loadCount()).isEqualTo(2);
    assertThat(stats.totalLoadTime()).isAtLeast(totalLoadTime);
    totalLoadTime = stats.totalLoadTime();

        assertEquals(SimpleCircuitBreaker.State.CLOSED, circuitBreaker.getState());

        SimpleCircuitBreaker.Statistics stats = circuitBreaker.getStatistics();
        assertEquals(1, stats.totalCalls);
        assertEquals(1, stats.totalSuccesses);
        assertEquals(0, stats.totalFailures);
        assertEquals(1.0, stats.successRate);
    }

    @Test
    @DisplayName("Test circuit opens after failure threshold")

    key = new Object();
    cache.refresh(key);
    checkNothingLogged();
    stats = cache.stats();
    assertThat(stats.missCount()).isEqualTo(2);
    assertThat(stats.loadSuccessCount()).isEqualTo(3);
    assertThat(stats.loadExceptionCount()).isEqualTo(0);
    assertThat(stats.hitCount()).isEqualTo(0);

    assertThat(cache.get(key)).isSameInstanceAs(key);
    stats = cache.stats();