assertThat(
            concat(megaPrimitiveDoubleStreamPart1(), megaPrimitiveDoubleStreamPart2())
                .sorted()
                .toArray())
        .isEqualTo(megaPrimitiveDoubleStream().toArray());
  }

  public void testAddAllPrimitiveDoubleStream() {
    StatsAccumulator accumulator = new StatsAccumulator();
    accumulator.addAll(megaPrimitiveDoubleStreamPart1());

  static DoubleStream megaPrimitiveDoubleStreamPart1() {
    return DoubleStream.iterate(0.0, x -> x + 2.0).limit(MEGA_STREAM_COUNT / 2).parallel();
  }

  /**
   * Returns a stream containing the values from {@link #megaPrimitiveDoubleStream} not in {@link
   * #megaPrimitiveDoubleStreamPart1()}.
   */
  static DoubleStream megaPrimitiveDoubleStreamPart2() {