birthday-sw-v4.rb

require "minitest/autorun"
require "date"

class Person
  attr_reader :birthday

  def initialize(attributes={})
    @birthday = attributes.fetch(:birthday)
  end

  def can_drink_in?(year)
    age_in(year) > 21
  end

  def age_in(year)
    year - birthday.year
  end

  def age_now
    age_in Date.new.year
  end
end

describe Person do
  let(:seventy_niner) do
    Person.new birthday: Date.new(1979)
  end

  it "age is determined by their birthday" do
    seventy_niner.age_in(2009).must_equal 30
  end

  it "can drink if older than 21" do
    seventy_niner.can_drink_in?(2009).must_equal true
  end

  it "age now is today" do
    seventy_niner.age_in(Date.new.year).must_equal seventy_niner.age_now
  end
end