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

require "test/unit"
require "stringio"
require "delegate"

class QuizIORecorder < DelegateClass(StringIO)
  
  attr_accessor :io, :log
  
  def initialize(log = [])
    @io = StringIO.new
    @log = log
    super(@io)
  end
  
  def gets
    s = @io.gets
    @log << [:gets, s]
    s
  end
  
  def puts(s)
    r = @io.puts(s)
    @log << [:puts, s]
    r
  end

end

class QuizTest < Test::Unit::TestCase
    
  def setup
    @seed = 42
    srand(@seed)
    @log = Array.new
    @input = QuizIORecorder.new(@log)
    @output = QuizIORecorder.new(@log)
    @quiz = Quiz.new(@input, @output)
  end
  
  def correct_answer
    srand(@seed)
    first = rand(10)
    second = rand(10)
    srand(@seed)
    first + second
  end
  
  def test_correct
    @input << correct_answer.to_s
    @input.rewind
    
    @quiz.problem

    assert_equal([:puts, :gets, :puts], @log.map { |e| e.first },
    "Quiz procedure occurred in the wrong order: gets occurred before puts")
    @output.rewind
    assert_equal("Correct!\n", @output.readlines.last, "Quiz did not report a correct response")
  end
  
  def test_incorrect
    @input << "-1"
    @input.rewind
    
    @quiz.problem

    assert_equal([:puts, :gets, :puts], @log.map { |e| e.first },
    "Quiz procedure occurred in the wrong order: gets occurred before puts")
    @output.rewind
    assert_equal("Incorrect!\n", @output.readlines.last, "Quiz did not report an incorrect response")
  end
end