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Gentlemen, Place Your Bets

I’m interested in moving on to building a user interface for the Texas Hold ’Em application. But we may want to start one last piece of functionality before going on. Right now, our application supports dealing cards to players as well as collecting their blinds. It doesn’t support any other sort of betting interaction, however.

We might be tempted to add the betting interaction tests and code to the Game class. Game is getting a bit large, however—something I’ve noted before. I think we’d be better off heeding the single-responsibility principle. An improved design direction would be to break relevant code out of Game into a Hand class. Code in the Hand class would manage flow within a given Texas Hold ’Em hand, the sequence of events from startHand to stopHand. Code in the Game class would manage overall table flow: adding players, initiating hands, rotating the deal, and so on. (Maybe this suggests Table as a better name for Game?)

Creating the separate Hand class is a larger refactoring step. We’ll take it as incrementally as possible, seeking positive feedback with each smaller step. A creation test is always a good place to start (see Listing 3). Initially, I think each hand will need to capture the current button position and set of players. Listing 4 shows the initial production Hand class.

Listing 3 Test-driving the creation of Hand.

package domain;

import java.util.*;
import junit.framework.*;

public class HandTest extends TestCase {
  public void testCreate() {
   final List<Player> players = new ArrayList<Player>();
   players.add(new Player("a"));
   players.add(new Player("b"));

   final int button = 1;

   Hand hand = new Hand(players, button);
   assertSame(players, hand.players());
   assertEquals(button, hand.button());
  }
}

Listing 4 Initial Hand implementation.

package domain;

import java.util.*;

public class Hand {
  private List<Player> players;
  private int button;

  public Hand(List<Player> players, int button) {
   this.players = players;
   this.button = button;
  }

  List<Player> players() {
   return players;
  }

  int button() {
   return button;
  }
}

So far, so simple. Next, let’s move code from GameTest into HandTest. Start with testDealCompleteHand. Copy the entire test method into HandTest, but don’t delete the test from GameTest yet. Getting this test to even compile will be a larger effort than we want to undertake in one step. Instead, we’ll comment out the body of the test, and then uncomment it up through the first assertion. The code in Listing 5 shows this refactoring, plus a few other changes made to take advantage of code from testCreate.

Listing 5 Incrementally moving tests to HandTest.

package domain;

import java.util.*;
import junit.framework.*;

public class HandTest extends TestCase {
  private List<Player> players;
  private int button;
  private Hand hand;
  private Player player1;
  private Player player2;
  private Deck deck;

  protected void setUp() {
   player1 = new Player("a");
   player2 = new Player("b");

   players = new ArrayList<Player>();
   players.add(player1);
   players.add(player2);

   button = 2;

   hand = new Hand(players, button);
  }

  public void testCreate() {
   assertSame(players, hand.players());
   assertEquals(button, hand.button());
  }

  public void testDealCompleteHand() {
   hand.start();

   deck = hand.deck();
   Card[] hole = deck.top(4);
   hand.dealHoleCards();

   assertHoleCards(player1, hole, 0, 2);
   assertHoleCards(player2, hole, 1, 3);
//
//   int remaining = Deck.SIZE - hole.length;
//   assertEquals(remaining, deck.cardsRemaining());
//   Card[] flop = deck.top(BURN + 3);
//
//   game.dealFlop();
//   remaining -= flop.length;
//   assertCardsDealt(remaining, flop);
//   CardTest.assertCards(game.community(),
//      flop[1], flop[2], flop[3]);
//
//   Card[] turn = deck.top(BURN + 1);
//   game.dealTurn();
//   remaining -= turn.length;
//   assertCardsDealt(remaining, turn);
//   CardTest
//      .assertCards(game.community(),
//      flop[1], flop[2], flop[3], turn[1]);
//
//   Card[] river = deck.top(BURN + 1);
//   game.dealRiver();
//   remaining -= river.length;
//   assertCardsDealt(remaining, river);
//   CardTest.assertCards(game.community(),
//      flop[1], flop[2], flop[3],
//      turn[1], river[1]);
  }

  private void assertHoleCards(Player player, Card[] hole, int... indices) {
   Card[] cards = new Card[indices.length];
   for (int i = 0; i < indices.length; i++)
     cards[i] = hole[indices[i]];
   DeckTest.assertCardsDealt(deck, cards);
   CardTest.assertCards(player.holeCards(), cards);
  }
}

After running this test and demonstrating expected failure, let’s move the production code into Hand. Listing 6 shows the changes.

Listing 6 Getting Hand up to date with the test.

...
public class Hand {
  ...
  private Deck deck;

  public void start() {
   deck = new Deck();
  }
  ...
  public Deck deck() {
   return deck;
  }

  public void dealHoleCards() {
   for (int round = 0; round < 2; round++) {
     for (int i = 1; i <= players.size(); i++) {
      Player player = getPlayer(button + i);
      player.dealToHole(deck.deal());
     }
   }
  }

  private int ringPosition(int position) {
   if (position > players.size())
     return position - players.size();
   return position;
  }

  private Player getPlayer(int position) {
   return players.get(ringPosition(position) - 1);
  }
}

Our tests should now pass. We’ll move on by proceeding in the same manner: Uncomment a bit of test, and move just enough code to make the test pass. Listing 7 shows the completed test method and its supporting utility methods. Listing 8 shows the modified production source.

Listing 7 Completed testDealCompleteHand.

public void testDealCompleteHand() {
  hand.start();

  deck = hand.deck();
  Card[] hole = deck.top(4);
  hand.dealHoleCards();

  assertHoleCards(player1, hole, 0, 2);
  assertHoleCards(player2, hole, 1, 3);

  int remaining = Deck.SIZE - hole.length;
  assertEquals(remaining, deck.cardsRemaining());
  Card[] flop = deck.top(BURN + 3);

  hand.dealFlop();
  remaining -= flop.length;
  assertCardsDealt(remaining, flop);
  CardTest.assertCards(hand.community(), flop[1], flop[2], flop[3]);

  Card[] turn = deck.top(BURN + 1);
  hand.dealTurn();
  remaining -= turn.length;
  assertCardsDealt(remaining, turn);
  CardTest
     .assertCards(hand.community(), flop[1], flop[2], flop[3], turn[1]);

  Card[] river = deck.top(BURN + 1);
  hand.dealRiver();
  remaining -= river.length;
  assertCardsDealt(remaining, river);
  CardTest.assertCards(hand.community(), flop[1], flop[2], flop[3],
     turn[1], river[1]);
}

private void assertHoleCards(Player player, Card[] hole, int... indices) {
  Card[] cards = new Card[indices.length];
  for (int i = 0; i < indices.length; i++)
   cards[i] = hole[indices[i]];
  DeckTest.assertCardsDealt(deck, cards);
  CardTest.assertCards(player.holeCards(), cards);
}

private void assertCardsDealt(int remaining, Card[] turn) {
  assertDeckCount(remaining);
  DeckTest.assertCardsDealt(deck, turn);
}

private void assertDeckCount(int expected) {
  assertEquals(expected, deck.cardsRemaining());
}

Listing 8 Updated Hand code to meet testDealCompleteHand.

...
public class Hand {
  ..
  private List<Card> community = new ArrayList<Card>();
  ...
  public void dealFlop() {
   burn();
   for (int i = 0; i < 3; i++)
     community.add(deck.deal());
  }

  private void burn() {
   deck.deal();
  }

  public List<Card> community() {
   return community;
  }

  public void dealTurn() {
   burnAndTurn();
  }

  public void dealRiver() {
   burnAndTurn();
  }

  private void burnAndTurn() {
   burn();
   community.add(deck.deal());
  }
}

One more change comes to mind: In testDealCompleteHand, explicitly calling the start method now seems unnecessary. Constructing a hand should result in the same actions as specified in the start method. Let’s remove the first line from testDealCompleteHand so that it looks like this:

public void testDealCompleteHand() {
  deck = hand.deck();

Then we’ll modify the Hand constructor to call the start method (which we can now make private).

public Hand(List<Player> players, int button) {
  this.players = players;
  this.button = button;
  start();
}

Now the fun part: We can remove code from Game and have it delegate over to Hand. Listing 9 shows the relevant parts.

Listing 9 Hand takes on responsibility from Game.

private Hand hand; // the declaration for "community" goes away

// needed for testing
Deck deck() {
  return hand.deck();
}

public void dealFlop() {
  hand.dealFlop();
}

public List<Card> community() {
  if (hand == null)
   return new ArrayList<Card>();
  return hand.community();
}

public void dealTurn() {
  hand.dealTurn();
}

public void dealRiver() {
  hand.dealRiver();
}

public void startHand() {
  collectBlinds();
  hand = new Hand(players, button);
}

public void dealHoleCards() {
  hand.dealHoleCards();
}

private void removeAllCards() {
  for (Player player: players())
   player.removeCards();
  hand = null;
}

We want to continue to move as much into HandTest and Hand as makes sense. This also includes tests and logic for extracting blinds.

Does GameTest still require a test for dealing a complete hand? Yes and no. The Game class provides the public interface that clients will use. So we still need to prove that Game does the right thing with messages sent to it. But perhaps we can simplify things and only prove that Hand gets delegated the proper messages. We have tests for Hand to prove that its details are correct and that Hand objects respond to those messages correctly:

public void testDealCompleteHand() {
  addTwoPlayers();
  game.setButton(2);
  startHand();

  Card[] hole = deck.top(4);
  game.dealHoleCards();

  assertHoleCards(player1, hole, 0, 2);
  assertHoleCards(player2, hole, 1, 3);

  Card[] community = deck.top(3 * BURN + 5);

  game.dealFlop();
  game.dealTurn();
  game.dealRiver();
  CardTest.assertCards(game.community(),
     community[1], community[2], community[3],
     community[5], community[7]);
}
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