simple LIFO, FIFO functions in ruby

lifo_fifo.rb

require "test/unit"

class Array
  def fifo
    verbrauch = inject(0) {|sum, el| sum+=el.abs if el < 0; sum }
    res = select{|el| el > 0}.inject([]) do |result, el|
      if el > verbrauch  
        result << (el - verbrauch)
        verbrauch = 0
      else
        result << 0 
        verbrauch -= el
      end
      result
    end
    res
  end
  def lifo
    inject([]) { |result, el| 
      if el < 0 
       res = (result.reverse + [el]).fifo.reverse
      else
       res = result + [el]
      end
      res
    }
  end 
end

p [5,-4,3,6,-2,11,-3,1,1].fifo
p [5,-4,3,6,-2,11,-3,1,1].lifo

class TestFiFo < Test::Unit::TestCase

  def test_0
    assert_equal([],[].fifo)
  end
  def test_1
    assert_equal([1,2],[1,2].fifo)
  end
  def test_2
    assert_equal([0,2], [1,2,-1].fifo)
    assert_equal([1,1], [1,2,-1].lifo)
  
  end
  def test_3
    assert_equal([0,2,3], [3,3,3,-4].fifo)
    assert_equal([3,2,0], [3,3,3,-4].lifo)
  end
  def test_loesung
    assert_equal([0, 0, 5, 11, 1, 1], [5,-4,3,6,-2,11,-3,1,1].fifo)
    assert_equal([1,3,4,8,1,1] , [5,-4,3,6,-2,11,-3,1,1].lifo)
  end
  
end