Orlando Ruby Coding Dojo - 3/8/2011

main.rb

require "enumerator"

class Solution
  include Enumerable
  
  def initialize ( cap=nil )
    @e = Enumerator.new do |yielder|
      a = b = 1
      loop do
        break if cap && b > cap
        yielder << b
        a, b = b, a + b
      end
    end
  end
  
  def each
    yield @e.next
  end
end #Solution

test.rb

#!/usr/bin/env ruby1.9

require "test/unit"
require_relative "main"

# Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the
# first 10 terms will be:
# 
# 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
# 
# By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the
# even-valued terms.
class SolutionTest < Test::Unit::TestCase
  def test_fib
    solution = Solution.new
    
    expected = [ 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 ]
    
    expected.each do |n|
      assert_equal n, solution.each
    end
  end
  
  def test_fib_with_cap
    solution = Solution.new 10
    
    expected = [ 1, 2, 3, 5, 8 ]
    
    expected.each do |n|
      assert_equal n, solution.each
    end
    
    assert_raise StopIteration do
      solution.each
    end
  end
  
  def test_solution
    actual = Solution.new(10).select do |n|
      n.even?
    end
    
    assert_equal [2, 8 ], actual
    
    assert_equal 0, Solution.new(4000000).select{|n| n.even? }.reduce(:+)
  end
end #SolutionTest