Background

Tonight we had our first coding Dojo at GeekUp Nottingham. Last month we had Peter Cooper (author of Beginning Ruby) along to teach us some Ruby in preparation. The idea was that we would all be on an equal footing to perform dojos.

The problem

Brucie’s play your cards right!

Poor Brucie is getting on a bit. He’s asked for a piece of software to help him figure out whether a card is higher or lower.We need you to write an app which will take two cards and tell you which is the highest. Ace is high.

If time enhance the game to have 5 random cards which are all unknown to user, but know to the program. Reveal first card, user guesses if next card is higher or lower. Reveal car and whether user was right. Carry on for all 5 cards. user has to get all cards right. Cards are selected from a deck of 52.

What we did

The focus of the dojo was on Test Driven Development and Pair Programming.

As we’re all quite new to Ruby, we’ll work together, with a pair at the front for five minutes, swap in a new person after the time has passed. The audience can participate by shouting out any help. This is called a Randori.

The first 30 minutes or so was spent learning how to do TDD in Ruby. It was pretty difficult, however having 12 people all learning and helping eachother was a really rewarding experience. We all learned, we all felt a sense of achievement when the code compiled. There were whoops and cheers when we made a failing test PASS!

The TDD learning experience worked well. The audience were very vocal, a lot of “woah woah WOAH”‘s, sharp intakes of breath, suggestions to improve, concerns over smells, reigning people in when they started to get a bit too ahead of themselves. It was pair programming on steroids.

The Code

Obviously we built this up, but this is what we ended up with:

require 'test/unit'

class CardIsHigherTest < Test::Unit::TestCase

  def test_7H_is_higher_than_3H_with_higher_card_first
    higher_card = RoboBrucie.which_is_higher('7H', '3H')
    assert_equal('7H', higher_card)
  end
  
  def test_7H_is_higher_than_3H_with_lower_card_first
    higher_card = RoboBrucie.which_is_higher('3H', '7H')
    assert_equal('7H', higher_card)
  end
  
  def test_2C_and_2H_return_nothing_for_a_pair_brucie_message
    message = RoboBrucie.which_is_higher('2C', '2H')
    assert_equal('You get nothing for a pair, not in this game.', message)
  end

  def test_6D_is_higher_than_2D_with_higher_card_first
    higher_card = RoboBrucie.which_is_higher('6D', '2D')
    assert_equal('6D', higher_card)
  end

  def test_KH_is_higher_than_QC_with_higher_card_first
    higher_card = RoboBrucie.which_is_higher('KH', 'QC')
    assert_equal('KH', higher_card)
  end

  def test_KS_is_higher_than_8C_with_lower_card_first
    higher_card = RoboBrucie.which_is_higher('8C', 'KS')
    assert_equal('KS', higher_card)
  end

  def test_10H_is_higher_than_5S_with_higher_card_first
    higher_card = RoboBrucie.which_is_higher('10H', '5S')
    assert_equal('10H', higher_card)
  end
end

class RoboBrucie
  def self.which_is_higher(first_card, second_card)
    if (first_card == '2C') then return 'You get nothing for a pair, not in this game.' end
    first_card_value = value_of(first_card)
    second_card_value = value_of(second_card)

    return first_card_value > second_card_value ? first_card : second_card

  end

  def self.value_of(card)
    rank = card[0..-2]
    case (rank)
      when 'K'
        return 13
      when 'Q'
        return 12
      else
        return rank.to_i
     end
  end
end

The retro

We mostly debated TDD. The benefits and shortcomings of this. We obviously have a lot of work to do in convincing people of TDD, so we’re going to repeat this next month. The origin of Kata’s come from Karate. Repeating the same moves over and over so that they become second nature in a fight situation. We’re going to solve the same problem next month, this will allow us to concentrate on improving our technique of TDD and programming in Ruby.