Figuring out the correct way to deal with FactoryGirl callbacks on a has_many association.

computer.rb

class Computer < ActiveRecord::Base
  validates :make, presence: true, length: { maximum: 23 }
  validates :model, presence: true, length: { maximum: 23 }
  #ESN or MEID lengths should be expected, but we'll use 23 just 'cuz
  validates :serial_number, presence: true, length: { maximum: 23 }
  belongs_to :customer
end

customer.rb

class Customer < ActiveRecord::Base
  validates :first_name, :last_name, presence: true, length: { maximum: 23 }
  validates :address, presence: true, length: { maximum: 95 }
  validates :phone_number, presence: true, 
    length: { maximum: 10 }, numericality: { only_integer: true }
  validates :zip_code, presence: true, 
    length: { maximum: 5 }, numericality: { only_integer: true }

  has_many :computers

  def full_name
    "#{self.first_name} #{self.last_name}"
  end
end

factories.rb

FactoryGirl.define do
  factory :customer do
    first_name "Finn"
    last_name "Human"
    phone_number "1112223333"
    address "19 Treehouse Way"
    zip_code "54321"

    factory :customer_with_computer do
      after(:build) do |customer|
        create(:computer, customer: customer)
      end
    end
  end

  factory :computer do
    make "Asus"
    model "X52F"
    serial_number "A8N0AS24571899E"
  end

end

viewing_computers_spec.rb

require 'spec_helper'

describe "Viewing Computers" do
  let!(:customer) { FactoryGirl.build(:customer_with_computer) }
  computer = FactoryGirl.create(:computer)

  before do
    visit '/'
    click_link "Customers"
    click_link customer.full_name
  end

  describe "the Customer profile page" do
    it "shows the list of Customer Computers" do
      expect(page).to have_content("Computers")
      expect(page).to have_link (computer.make + " " + computer.model)
    end
  end

  describe "clicking on a Computer" do
    it "shows the Computer specs" do
      click_link (computer.make + " " + computer.model)
      expect(page).to have_content(computer.make)
      expect(page).to have_content(computer.model)
      expect(page).to have_content(computer.serial_number)
    end
  end
end