DrinkingGame.php

<?php

class DrinkingGame
{
    const TAIL = 'tail';
    const DRUNKEST = 'zoltan';
    
    public function __construct(array $names, Coin $coin = null) {
        $this->names = array_fill_keys($names, 0);
        $this->coin = $coin;
    }
    
    public function getDrinkList($tosses)
    {
        for ($i = 0; $i < $tosses; $i++) {
            $coinflips = $this->coin->toss();
            if (self::TAIL === $coinflips[0] && self::TAIL === $coinflips[1]) {
                foreach ($this->names as $name => $count) {
                    $this->names[$name]++;
                }
            } else if ($coinflips[0] !== $coinflips[1]) {
                $this->names[self::DRUNKEST]++;
            }
        }
        
        return $this->names;
    }
}

DrinkingGameTest.php

<?php

require_once "DrinkingGame.php";

class DrinkingGameTest extends \PHPUnit_Framework_TestCase
{
    private $coin;
    
    public function setUp()
    {
        $this->coin = $this->getMock('Coin', ['toss']);
    }
    
    public function testNoTossesAndNoPeopleGetEmptyList() {
        $drinkingGame = $this->getDrinkingGame([]);
        
        $drinkList = $drinkingGame->getDrinkList(0);
        
        $this->assertEquals([], $drinkList);
    }
    
    public function testWithPeopleButNoTossesGetsPeopleListWithZeroDrinks()
    {
        $drinkingGame = $this->getDrinkingGame(['lassi']);
        
        $drinkList = $drinkingGame->getDrinkList(0);
        
        $this->assertEquals(['lassi' => 0], $drinkList);
    }
    
    public function testTwoTailsEveryoneDrinksOne()
    {
        $this->givenCoinsAlwaysTailAndTail();
        
        $drinkingGame = $this->getDrinkingGame(['lassi', 'eralp']);
        
        $drinkList = $drinkingGame->getDrinkList(1);
        
        $this->assertEquals(['lassi' => 1, 'eralp' => 1], $drinkList);
    }
    
    public function testTwoDifferentZoltanDrinksOne()
    {
	    $this->givenCoinsAlwaysTailAndHeads();
        
        $drinkingGame = $this->getDrinkingGame(['zoltan', 'eralp']);
        
        $drinkList = $drinkingGame->getDrinkList(1);
        
        $this->assertEquals(['zoltan' => 1, 'eralp' => 0], $drinkList);
    }
    
    public function testHeadsAndHeadsNoOneDrinks()
    {
        $this->givenCoinsAlwaysHeadsAndHeads();
        $drinkingGame = $this->getDrinkingGame(['zoltan', 'eralp']);
        $drinkList = $drinkingGame->getDrinkList(1);

        $this->assertEquals(['zoltan' => 0, 'eralp' => 0], $drinkList);
    }
    
    public function testTwoTailsTwiceEveryoneDrinksTwice()
    {
        $this->givenCoinsAlwaysTailAndTail();
        
        $drinkingGame = $this->getDrinkingGame(['lassi', 'eralp']);
        
        $drinkList = $drinkingGame->getDrinkList(2);
        
        $this->assertEquals(['lassi' => 2, 'eralp' => 2], $drinkList);
    }
    
    public function testO()
    {
        $this->givenCoinflipOrder([['tail', 'tail'], ['tail', 'heads']]);
        
        $drinkingGame = $this->getDrinkingGame(['zoltan', 'eralp']);
        
        $drinkList = $drinkingGame->getDrinkList(2);
        
        $this->assertEquals(['zoltan' => 2, 'eralp' => 1], $drinkList);
    }
    
    private function getDrinkingGame(array $names) 
    {
         return new DrinkingGame($names, $this->coin);
    }
    
    private function givenCoinflipOrder(array $coinflips) 
    {
        $this->coin->expects($this->any())
			->method('toss')
			->will(new \PHPUnit_Framework_MockObject_Stub_ConsecutiveCalls($coinflips));
    }
    
    private function givenCoinsAlwaysTailAndHeads() 
    {
        $this->coin->expects($this->any())
			->method('toss')
			->will($this->returnValue(['tail', 'heads']));
    }
    
    private function givenCoinsAlwaysTailAndTail()
    {
        $this->coin->expects($this->any())
			->method('toss')
			->will($this->returnValue(['tail', 'tail']));
    }
    
    private function givenCoinsAlwaysHeadsAndHeads()
    {
        $this->coin->expects($this->any())
			->method('toss')
			->will($this->returnValue(['heads', 'heads']));
    }
}