gistfile1.rb

# This one works
class DiceSet

  def roll(size)
    @dice = []
    size.times do |x|
        @dice[x] = rand(1..6)
    end
  end

  def values
    @dice
  end

end

vs

# This one doesn't (i.e., the test fails) - when run from within the koan test
# It totally works fine when run in irb
class DiceSet

  def initialize
     @dice = []
  end
  
  def roll(size)
   
    size.times do |x|
        @dice[x] = rand(1..6)
    end
  end

  def values
    @dice
  end

end

def test_dice_values_should_change_between_rolls
  dice = DiceSet.new

  dice.roll(5)
  first_time = dice.values

  dice.roll(5)
  second_time = dice.values

  assert_not_equal first_time, second_time,
    "Two rolls should not be equal"
end

That makes a ton of sense, Carlo. Thanks!