quiz.rb

# COMMUNITY CHALLENGE
#
# How would you test this Quiz#problem method? Only two rules:
#
# 1. No mocks or stubs allowed. I'm looking for a other alternatives.
# Mocks can get messy in complex scenarios, and this is intended to
# be a high level test which executes all code. I don't think mocking
# would be a very clean solution anyway, but if you want to try it
# and prove me wrong feel free.
#
# 2. No changing the Quiz class implementation/structure. But you can
# use whatever framework you want for the tests.
#
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

require "test/unit"
require "stringio"

class QuizTest < Test::Unit::TestCase
  
  Kernel.module_eval do
    def rand(n)
      @rand ||= [1,2]
      @rand.shift or raise
    end
  end
  
  def test_correct
    @input = StringIO.new('3', 'r')
    @output = StringIO.new('', 'w')
    
    Quiz.new(@input, @output).problem
    assert_equal "What is 1 + 2?\nCorrect!\n", @output.string
  end
  
  def test_incorrect
    @input = StringIO.new('jello', 'r')
    @output = StringIO.new('', 'w')
    
    Quiz.new(@input, @output).problem
    assert_equal "What is 1 + 2?\nIncorrect!\n", @output.string
  end
end