question.rb

class Question
  CHARS = ("a".."z").to_a

  attr_accessor :description
  attr_writer :right_answer, :chosen_answer

  [:right_answer, :chosen_answer].each do |name|
    class_eval <<-RUBY
      def #{name}(*args)
        @#{name} = args.first if args.any?
        @#{name}
      end
    RUBY
  end

  def initialize(description = nil)
    @description = description
  end

  def alternatives
    @alternatives ||= []
  end

  def alternative(description)
    alternatives << description
  end

  def shuffle!
    @alternatives.shuffle!
  end

  def to_s
    String.new.tap do |s|
      s << description << "\n"
      s << alternatives.each_with_index.collect {|a, i| build_alternative(i)}.join
    end
  end

  def right?
    right_answer && chosen_answer && right_answer == chosen_answer
  end

  private
  def build_alternative(index)
    String.new.tap do |s|
      s << CHARS[index] << ") " << alternatives[index].to_s
      s << " √" if chosen_answer == alternatives[index] && right?
      s << "\n"
    end
  end
end

def Question(description, &block)
  Question.new(description).tap do |question|
    question.instance_eval(&block)
  end
end

if $0 == __FILE__
  require "mocha"
  require "test/unit"

  class QuestionTest < Test::Unit::TestCase
    def setup
      @question = Question.new("2 + 2?")
    end

    def test_set_description_from_initializer
      assert_equal "My question", Question.new("My question").description
    end

    def test_set_right_answer
      @question.right_answer = "Right answer"
      assert_equal "Right answer", @question.right_answer

      @question.right_answer("Correct answer")
      assert_equal "Correct answer", @question.right_answer
    end

    def test_set_chosen_answer
      @question.chosen_answer = "My answer"
      assert_equal "My answer", @question.chosen_answer

      @question.chosen_answer("Chosen answer")
      assert_equal "Chosen answer", @question.chosen_answer
    end

    def test_set_new_alternative
      @question.alternative 1
      @question.alternative 2
      @question.alternative 3

      assert_equal 3, @question.alternatives.size
      assert_equal 1, @question.alternatives[0]
      assert_equal 2, @question.alternatives[1]
      assert_equal 3, @question.alternatives[2]
    end

    def test_shuffle_alternatives
      @question.alternatives.expects(:shuffle!).once
      @question.shuffle!
    end

    def test_readable_question
      @question.alternative(4)
      @question.alternative(5)
      @question.alternative("I'm not into that Math thing")
      str = @question.to_s

      assert_match /2 \+ 2\?\n/, str
      assert_match /[a-c]\) 4\n/, str
      assert_match /[a-c]\) 5\n/, str
      assert_match /[a-c]\) I'm not into that Math thing\n/, str
    end

    def test_mark_write_answer
      @question.alternative(4)
      @question.alternative(5)
      @question.alternative(6)

      @question.chosen_answer(4)
      @question.right_answer(4)

      assert_match /[a-z]\) 4 √/u, @question.to_s
      assert_no_match /5 √/, @question.to_s
      assert_no_match /6 √/, @question.to_s
    end

    def test_right_question
      @question.chosen_answer(4)
      @question.right_answer(4)
      assert @question.right?
    end

    def test_wrong_question
      @question.chosen_answer(4)
      @question.right_answer(6)
      assert !@question.right?
    end
    
    def test_dsl_method
      question = Question("2 + 2?") do
        alternative 4
        alternative 5
        alternative 6
        
        right_answer 4
        chosen_answer 7
      end
      
      assert_equal "2 + 2?", question.description
      assert_equal 4, question.right_answer
      assert_equal 7, question.chosen_answer
      assert_equal [4,5,6], question.alternatives
    end
  end
end