public void PartitionBy_WithEmptyEnumerableAndEmptyCount_Throws()
 => Throws <ArgumentOutOfRangeException>(
     () => ENMRBL_EMPTY.PartitionBy(0).ToList());
 public void PartitionBy_WithEmptyEnumerableAndNegativeCount_Throws()
 => Throws <ArgumentOutOfRangeException>(
     () => ENMRBL_EMPTY.PartitionBy(-COUNT_ANY).ToList());