The pad mapper problem

pad_mapper_test.rb

#  Given an input string of 0 or more digits '2' - '9', list out all the possible strings
# from a typical phonepad digit-to-letter conversion (below), one per line
#
# 2: ABC 3: DEF 4: GHI 5: JKL 6: MNO 7: PQRS 8: TUV 9: WXYZ 

LETTERS = [%w(A B C), %w(D E F), %w(G H I), %w(J K L), %w(M N O), %w(P Q R S), %w(T U V), %w(W X Y Z)]

def pad_mapper(*numbers)
  # Fill me out!
end

describe '#pad_mapper' do
  context 'When given two digits with three letter keys' do
    it 'returns nine results as letter pairs' do
      expect(pad_mapper(2,3)).to eq(%w(
        AD AE AF
        BD BE BF
        CD CE CF
      ))
    end
  end

  context 'When given two digits with one three letter and one four letter key' do
    it 'returns twelve results' do
      expect(pad_mapper(3,7)).to eq(%w(
        DP EP FP
        DQ EQ FQ
        DR ER FR
        DS ES FS
      ))
    end
  end
end