Array Flattener + Tests

array_flattener.rb

#!/usr/bin/ruby

class ArrayFlattener
  def initialize(array)
    @array = array
  end

  def call
    raise unless array.is_a? Array

    # The next line does the following:
    # 1 - converts the array to a string
    # 2 - scans the code looking for numbers using regex
    # 3 - convert the array of string numbers found to an array of integers
    array.to_s.scan(/\d+/).map(&:to_i)
  end

  private

  attr_reader :array
end

tc_array_flattener.rb

require_relative 'array_flattener'
require 'test/unit'

class TestArrayFlattener < Test::Unit::TestCase
  def test_base
    assert_equal([1,2,3,4], ArrayFlattener.new([[1,2,[3]],4]).call)
  end

  def test_no_change
    assert_equal([1,2,3,4], ArrayFlattener.new([1,2,3,4]).call)
  end

  def test_simple
    assert_equal([1,2,3,4], ArrayFlattener.new([[1],[2],[3],[4]]).call)
  end

  def test_big_numbers
    assert_equal([111,222222,33333333,4444444], ArrayFlattener.new([[111,222222,[33333333]],4444444]).call)
  end

  def test_multiple_levels
    assert_equal([1,2,3,4], ArrayFlattener.new([[[[[1],[2]],[3]],[4]]]).call)
  end

  def test_typecheck
    assert_raise( RuntimeError ) { ArrayFlattener.new(1).call }
  end
end