score_test.rb

require 'rubygems'
require "test/unit"
require "shoulda"

def score(roll)
  accum = 0
  
  raise ArgumentError unless roll.is_a? Array
  raise RuntimeError unless roll.any?{|r| r.is_a? Fixnum }
  raise RuntimeError if roll.any?{|r| r < 1}
  
  accum += 100 if single_detector(roll, 1)
  accum += 50 if single_detector(roll, 5)

  (1..6).each do |num|
    if roll.find_all{|n| num == n}.length >= 3
      score = num == 1 ? 1000 : 100      
      accum += score * num
    end
  end

  accum
end 

def single_detector(roll, number)
  roll.find_all{|n| n == number}.length == 1
end

def assert_score(score, roll)
  assert_equal(score, score(roll))
end

class TestGreed < Test::Unit::TestCase

  context "with valid data" do    
    context "a single die" do
      should "score 100 if 1" do
        assert_score(100, [1])
      end    
      should "score 50 if 5" do        
        assert_score(50, [5])
      end
    end

    should "score triples as 100 * the triple unless it is 1" do
      assert_score(300, [3,3,3])
      assert_score(400, [4,4,4])
      assert_score(500, [5,5,5])
    end

    should "score triple 1's as 1000" do
      assert_score(1000, [1,1,1])
    end

    should "score 3,4,2,4,4 as 400" do
      assert_score(400, [3,4,2,4,4])
    end

    should "score 4,4,4,4,1 as 400" do
      assert_score(500, [4,4,4,4,1])
    end

    should "score 2,1,1,3,1" do
      assert_score(1000, [2,1,1,3,1])
    end
  end
  
  context "with invalid data" do
    should "raise an ArgumentError if an array is not passed" do
      assert_raise(ArgumentError) do
        score("a bad string")
      end
    end
    
    should "raise a RuntimeError if the array contains non integers" do
      assert_raise(RuntimeError) do
        score(%w[a b c 1 3])
      end
    end
    
    should "raise a RuntimeError if the array contains negative numbers" do
      assert_raise(RuntimeError) do
        score([-1])
      end
    end
  end
end