CreditCard class

credit_card.rb

class CreditCard
  include ActiveAttr::Model
  attribute :number
  attribute :expiry
  attribute :cvn
  attribute :name

  validate :must_be_valid
  validates :number, :expiry, :cvn, :name, presence: true

  def expiry_month
    return nil unless expiry
    expiry.match(/(\d+)/).try(:[], 1).try(:to_i)
  end
  def expiry_year
    return nil unless expiry
    year = expiry.match(/(\d+)(\s|\/|\\|-)+(\d{2,4})/)[3].to_i
    year <= 99 ? 2000+year : year
  end

  def number_valid?
    return false unless self.number
    self.number =~ /^(\d|\s|-){5,25}$/
  end

  def expiry_valid?
    return false unless self.expiry
    return false unless (1..12).include? expiry_month
    return false if expiry_year < 2012
    true
  end

  def must_be_valid
    errors.add(:number, 'should be a valid credit card number') unless number_valid?
    errors.add(:expiry, 'should be a valid MM/YY') unless expiry_valid?
  end
end

credit_card_spec.rb

require 'faster_helper'
require 'active_attr'
require 'credit_card'
require 'shoulda-matchers'

describe CreditCard do
  its(:number) { should be_nil }
  its(:expiry) { should be_nil }
  its(:cvn) { should be_nil }
  its(:name) { should be_nil }

  describe "#expiry_month" do
    {
      '12/1111' => 12,
      '1/1111' => 1,
      '1-1111' => 1,
      '5/1111' => 5,
      ' 5 / 1111 ' => 5,
      '' => nil,
      ' ' => nil,
      nil => nil
    }.each_pair do |expiry, month|
      it "should be #{month} for #{expiry}" do
        CreditCard.new(:expiry => expiry).expiry_month.should == month
      end
    end
  end

  describe "#expiry_year" do
    {
      '5/2012' => 2012,
      '1-1111' => 1111,
      '1/1111' => 1111,
      '5/15' => 2015,
      ' 5 / 2012 ' => 2012,
      nil => nil
    }.each_pair do |expiry, year|
      it "should be #{year} for #{expiry}" do
        CreditCard.new(:expiry => expiry).expiry_year.should == year
      end
    end
  end
  it { should allow_value('4444333322221111').for :number }
  it { should allow_value(' 4444333322221111 ').for :number }
  it { should allow_value('4444-3333 2222 - 1111').for :number }
  it { should_not allow_value('xxx').for :number }
  it { should_not allow_value(' ').for :number }
  it { should_not allow_value('4444333322221111'*20).for :number }

  it { should allow_value('12/2012').for :expiry }
  it { should allow_value('12-2012').for :expiry }
  it { should allow_value('12 / 2012').for :expiry }
  it { should_not allow_value('13/13').for :expiry }
end