Generates and Validates banks Routing numbers

routing_number.rb

require 'rubygems'
require 'faker'

def generate_routing_number
  valid = false
  until valid
    number = Faker::Number.number(9).to_s
    valid = valid_routing_number? number
  end
  number
end

def valid_routing_number? routing_number
  d = routing_number.to_s.split('').map(&:to_i).select { |d| (0..9).include?(d) }
  case d.size
    when 9 then
      checksum = ((3 * (d[0] + d[3] + d[6])) +
                  (7 * (d[1] + d[4] + d[7])) +
                       (d[2] + d[5] + d[8])) % 10
      case checksum
        when 0 then true
        else        false
      end
    else false
  end
end