quiz.rb

# COMMUNITY CHALLENGE
#
# How would you test this Quiz#problem method? No mocks/stubs allowed.
#
# (Here's @seacreature's take)

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 "stringio"
require "test/unit"

class Input
  def initialize(output)
    @output = output
    @handler = nil
  end

  def handle_output(pattern, &block)
    @handler = [pattern, block]
  end

  def gets
     pattern, block = @handler
     block[@output.string.match(pattern)]
  end
end

class QuizTest < Test::Unit::TestCase

  def setup
     @output = StringIO.new
     @input  = Input.new(@output)
     @quiz   = Quiz.new(@input, @output)
  end

  def test_correct
    @input.handle_output /What is (\d) \+ (\d)/ do |m|
      m[1].to_i + m[2].to_i
    end
    
    @quiz.problem

    assert_equal "Correct!\n", @output.string.to_a.last
  end
  
  def test_incorrect
    @input.handle_output /What is (\d) \+ (\d)/ do |m|
      m[1].to_i + m[2].to_i - 1
    end

    @quiz.problem
    assert_equal "Incorrect!\n", @output.string.to_a.last
  end

end