fails:Array#permutation when no block is given returned Enumerator size with an array size greater than 0 returns the descending factorial of array size and given length
fails:Array#permutation when no block is given returned Enumerator size with an array size greater than 0 returns the descending factorial of array size with array size when there's no param
fails:Array#permutation when no block is given returned Enumerator size with an empty array returns 1 when the given length is 0
fails:Array#permutation when no block is given returned Enumerator size with an empty array returns 1 when there's param
