a ruby method that flatten an array with associated test

flatten_array.rb

def flatten_array(ary, result = [])
  raise 'Please pass an array as argument' unless ary.kind_of? Array

  # if an element in the given array is an array, recursively call flatten_array
  # on the element, otherwise push it into the result array
  ary.each do |ele|
    if ele.class == Array
      flatten_array(ele, result)
    else
      result << ele
    end
  end

  result
end

require 'test/unit'

class FlattenArrayTest < Test::Unit::TestCase
  ARRAY1 = [1, [2, 3, [4, 5]]]
  RESULT1 = [1, 2, 3, 4, 5]

  ARRAY2 = [[1, 2, [3]], 4]
  RESULT2 = [1, 2, 3, 4]

  def test1
    result = flatten_array(ARRAY1)
    assert_equal RESULT1, result, "Expect the result to be #{RESULT1}"
  end

  def test2
    result = flatten_array(ARRAY2)
    assert_equal RESULT2, result, "Expect the result to be #{RESULT2}"
  end
end