Check if two words are anagram in Ruby

anagram.rb

class Anagram
  def is_anagram?(one, other)
    one.downcase.chars.sort.join == other.downcase.chars.sort.join
  end
end

require 'minitest/autorun'

describe Anagram do
  before do
    @anagram = Anagram.new
  end

  describe '.is_it?' do
    describe 'when asked if it is an anagram' do
      it 'must respond positively' do
        one = 'amor'
        other = 'roma'

        @anagram.is_anagram?(one, other).must_equal true
      end
    end

    describe 'when asked if a capital letter is an anagram' do
      it 'must respond positively' do
        one = 'Celia'
        other = 'Alice'

        @anagram.is_anagram?(one, other).must_equal true
      end
    end
  end
end