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"

class QuizTest < Test::Unit::TestCase
  
  def test_correct
    c = CollectorAccuracy.new(0, "Correct!")
    @quiz = Quiz.new(c,c)
    @quiz.problem
  end
  
  def test_incorrect
    c = CollectorAccuracy.new(1, "Incorrect!")
    @quiz = Quiz.new(c,c)
    @quiz.problem
  end
  
  def test_sequence
    c = Collector.new(4)
    @quiz = Quiz.new(c,c)
    @quiz.problem        
  end
end

class Collector 
  def initialize(return_gets)
    @return_gets = return_gets
    @puts = 0
  end

  def gets
    fail("Puts is zero") if @puts == 0
    @return_gets
  end  

  def puts(value)    
    @puts += 1
  end
  
end

class CollectorAccuracy 
  def initialize(difference, expected)
    @puts = 0
    @difference = difference
    @expected = expected
  end
  
  def gets
    @answer
  end  

  def puts(value)
    @puts += 1
    
    if @puts == 1

      values = value.split
      first = values[2]
      second = values[4]
    
      @answer = first.to_i + second.to_i + @difference
    else
      
      fail(value) unless value == @expected
    end
  end
end

solutions.txt

SOLUTIONS

There are many ways to solve this problem. If you come up with more let me know
and I'll add them here.

Custom IO Class

  This was by far the most common solution. It involves creating a class which
  has its own "puts" method to record the output and a "gets" method to calculate
  the proper response based on that output.
  
  Overall this is an elegant solution. The only thing I don't care for is that
  it requires all logic to be set up front and the @quiz.problem call must
  happen at the end.
  
  Favorites:
  1. http://gist.github.com/112547 by matflores
  2. http://gist.github.com/112378 by ljsc
  3. http://gist.github.com/112309 by sandal


Mocking Methods

  This was originally against the rules because I was looking for other
  creative alternatives which mimicked the user at a higher level and cared
  little about the implementation. However, the mocking solution proved cleaner
  than I originally expected. It also provided the most helpful error messages
  when the app broke (if the order got switched, etc.).
  
  Like the previous solution the @quiz.problem is called at the end. It also has
  some dependencies on the implementation, specifically the "rand" method must
  be stubbed. IMO this is acceptable but might become an issue in more complex
  scenarios where more would need to be stubbed.
  
  Favorites:
  1. http://gist.github.com/112300 by intinig
  2. http://gist.github.com/112411 by jimweirich


Separate Thread or Process

  Here the Quiz#problem runs in a separate thread or process. I consider it to be
  a higher level test than the others because it is the closest to mimicking a real
  user. The @quiz.problem is called first and the test assertions happen live as it
  is running.
  
  I was hoping to see a few more experimentations along this line. You can see my
  take on the problem below which uses a separate generic class to handle the dirty
  work and leaves the test implementation very clean and self contained.
  
  Favorites:
  1. http://gist.github.com/112476 by ryanb
  2. http://gist.github.com/112326 by nimbletechnique