scrabble_spec.rb

module Scoring
  def self.included(base)
    base.class_eval do
      let(:__score_keeper) { ScoreKeeper.new }
      extend ScoreHelpers
      include ScoreMatchers
    end
  end

  class ScoreKeeper
    def initialize()
      @scores = Hash.new(0)
    end

    def assign_score(letter, value)
      @scores[letter.upcase] = value
    end

    def score_for(letter)
      @scores[letter.upcase]
    end
  end

  module ScoreHelpers
    def the_letter(letter, options)
      score = options[:is_worth]
      before { __score_keeper.assign_score(letter, score) }
    end
  end

  module ScoreMatchers
    extend RSpec::Matchers::DSL
 
    matcher :score do |expected_score| 
      def score_for(word)
        word.chars.map { |c| __score_keeper.score_for(c) }.inject(0, :+)
      end
 
      match do |word|
        score_for(word) == expected_score
      end
    end
  end
end
 
describe 'Scrabble' do
  include Scoring
 
  context 'with the letters D, O and G' do
    the_letter 'D', is_worth: 2
    the_letter 'O', is_worth: 1
    the_letter 'G', is_worth: 2
 
    specify { expect('DOG').to score 5 }
 
    context 'with the letter E' do
      the_letter 'E', is_worth: 1
 
      specify { expect('DOGE').to score 6 }
    end
  end
 
  context 'with the letters C, A and T' do
    the_letter 'C', is_worth: 3
    the_letter 'A', is_worth: 1
    the_letter 'T', is_worth: 1
 
    specify { expect('CAT').to score 5 }
 
    context 'with C on a triple letter score' do
      the_letter 'C', is_worth: 9
 
      specify { expect('CAT').to score 11 }
    end
  end
end