anagram_generator.rb

class AnagramGenerator
  attr_accessor :word, :words, :letters
  def initialize(word)
    @word = word
    @words = []
  end

  def generate
    if word == ''
      raise ArgumentError, "It can't be a blank string"
    else
      words = split_word_to_letter.permutation.map(&:join)
      words.shift
    end
    words
  end

  def split_word_to_letter
    letters = word.split('')
    letters
  end
end

anagram_generator_rspec.rb

require_relative 'anagram_generator.rb'

describe AnagramGenerator do

  it 'returns an argument message if a blanks string is passed' do
    expect { AnagramGenerator.new('').generate }.to raise_error(ArgumentError, "It can't be a blank string")
  end

  it 'should return the letter if it is only 1 letter' do
    expect(AnagramGenerator.new("h").generate).to eql ([])
  end

  it 'should takes a 2 letter word and create 2 word' do
    expect(AnagramGenerator.new('ab').generate).to eql (['ba'])
  end

  it 'should takes a 3 letter word and create 5 word' do
    expect(AnagramGenerator.new('dog').generate).to include('dgo','odg','ogd','god','gdo')
  end
end