Create a small script that rotates elements without using rotate method (ruby)

array_rotation.rb

require 'rspec'

# Returns a new array with the rotated positions
# when the count is major to one I'm going to call the divmod method
#
# Finally the result has summed the elements with different positions based on divmod method.
#
#
# @param ary [Array<Integer>]
# @param count [Integer]
#
# @return [Array<Integer>, String] the new array or message
#
def array_rotation(ary, count = 1)
  return 'It is an empty array' unless ary.length > 0

  divmod = count.divmod(ary.length)[1]
  ary.last(ary.length - divmod) + ary.first(divmod)
end

describe '#array_rotation' do
  context 'when an array is empty' do
    it 'returns a message' do
      expect(array_rotation([], 2)).to eq('It is an empty array')
    end
  end

  context 'when an array is not empty' do
    it 'when the rotation size is empty but default it must rotate once' do
      expect(array_rotation([1,2,3,4])).to eq([2,3,4,1])
    end

    it 'when the rotation size is negative' do
      expect(array_rotation([1,2,3,4], -2)).to eq([3,4,1,2])
    end

    it 'when the rotation size is 2' do
      expect(array_rotation([1,2,3,4], 2)).to eq([3,4,1,2])
    end

    it 'when the rotation size is 10' do
      expect(array_rotation([1,2,3,4], 10)).to eq([3,4,1,2])
    end

    it 'when the rotation size is impar' do
      expect(array_rotation([1,2,3,4], 5)).to eq([2,3,4,1])
    end

    it 'when the rotation size is a big number' do
      expect(array_rotation([1,2,3,4], 500000000000000001)).to eq([2,3,4,1])
    end
  end
end