quiz.rb

# COMMUNITY CHALLENGE
#
# How would you test this Quiz#problem method? Only two rules:
#
# 1. The tests should fail if any part of the application breaks.
#    For example: If "gets" is moved before "puts" then the tests should
#    fail since that breaks the application.
#
# 2. You cannot change the Quiz class. But you can use whatever framework
#    and tools you want for the tests. (RSpec, Cucumber, etc.)
# 
# Note: The first rule used to be "no mocking" but I changed it. If you
#       can accomplish the first rule with mocks then go ahead. I'm looking
#       for the simplest/cleanest solution whatever that may be.
#
class Quiz
  def initialize(input = STDIN, output = STDOUT)
    @input = input
    @output = output
  end
  
  def problem
    first = rand(10)
    second = rand(10)
    @output.puts "What is #{first} + #{second}?"
    answer = @input.gets
    if answer.to_i == first + second
      @output.puts "Correct!"
    else
      @output.puts "Incorrect!"
    end
  end
end


######################################################################
# SOLUTION 1 - Using no mocks
######################################################################

require 'rubygems'
require 'test/unit'
require 'shoulda'

class QuizTestWithoutMocks < Test::Unit::TestCase
  class PassingIO
    attr_reader :response
    attr_writer :correct_answer

    def initialize
      @correct_answer = true
    end

    def puts(str)
      if str =~ /What is (\d+) \+ (\d+)\?/
        @answer = calculate_answer($1.to_i, $2.to_i)
      else
        @response = str
      end
    end

    def gets
      "#{@answer}\n"
    end

    private

    def calculate_answer(first, second)
      if @correct_answer
        first + second
      else
        first + second + 1
      end
    end
  end

  context 'A Quiz' do
    setup do
      @io = PassingIO.new
      @quiz = Quiz.new(@io, @io)
    end
    
    context 'when given the correct answer' do
      setup do
        @io.correct_answer = true
        @quiz.problem
      end
      should 'get a Correct response' do
        assert_equal "Correct!", @io.response
      end
    end

    context 'when given an incorrect answer' do
      setup do
        @io.correct_answer = false
        @quiz.problem
      end
      should 'get a Incorrect response' do
        assert_equal "Incorrect!", @io.response
      end
    end
  end
end