my_flatten.rb

require 'minitest/autorun'
class ArrayUtil
  attr_reader :array

  def initialize(array)
    @array = array
  end

  def super_flatten
    @result = []
    recursive_flat @array
    @result
  end

  private

  def recursive_flat array
    array.each do |item|
      if item.is_a? Array
        recursive_flat item
      else
        @result << item
      end
    end
  end
end


class TestSuperFlatten < Minitest::Test
  def test_multiple_array
    test_array = [[1,2,[3]],4]
    result = ArrayUtil.new(test_array).super_flatten
    assert_equal [1,2,3,4], result
  end

  def test_simple_array
    test_array = [1,3,5,[6,7]]
    result = ArrayUtil.new(test_array).super_flatten
    assert_equal [1,3,5,6,7], result
  end

  def test_empty_array
    test_array = []
    result = ArrayUtil.new(test_array).super_flatten
    assert_equal [], result
  end
end