code refactor

spec/example_app/app/models/country.rb

@@ -1,4 +1,3 @@
 class Country < ActiveRecord::Base
-  validates :code, presence: true
-  validates :name, presence: true
+  validates :code, :name, presence: true
 end

spec/example_app/db/migrate/20170331144723_create_countries.rb

@@ -1,12 +1,11 @@
 class CreateCountries < ActiveRecord::Migration
   def change
     create_table :countries do |t|
-      t.string :code
+      t.string :code, null: false, index: { unique: true }
       t.string :name
 
       t.timestamps null: false
     end
-    add_index :countries, :code, unique: true
     add_column :customers, :country_code, :string, index: true
   end
 end

spec/example_app/db/seeds.rb

@@ -12,30 +12,34 @@
 Product.destroy_all
 Country.destroy_all
 
-Country.create(code: "US", name: "USA")
-Country.create(code: "CA", name: "Canada")
-Country.create(code: "CN", name: "China")
-Country.create(code: "RU", name: "Russia")
-Country.create(code: "AU", name: "Australia")
+countries = Country.create! [
+  { code: "US", name: "USA" },
+  { code: "CA", name: "Canada" },
+  { code: "CN", name: "China" },
+  { code: "RU", name: "Russia" },
+  { code: "AU", name: "Australia" },
+]
 
-100.times do
+customer_attributes = Array.new(100) do
   name = "#{Faker::Name.first_name} #{Faker::Name.last_name}"
-  Customer.create(
+  {
     name: name,
     email: Faker::Internet.safe_email(name),
-    country: Country.first,
-  )
+    country: countries.sample,
+  }
 end
 
+customers = Customer.create!(customer_attributes)
+
 product_attributes = YAML.load_file(Rails.root.join('db/seeds/products.yml'))
 
 product_attributes.each do |attributes|
-  Product.create attributes.merge(price: 20 + rand(50))
+  Product.create! attributes.merge(price: 20 + rand(50))
 end
 
-Customer.all.each do |customer|
+customers.each do |customer|
   (1..3).to_a.sample.times do
-    order = Order.create(
+    order = Order.create!(
       customer: customer,
       address_line_one: Faker::Address.street_address,
       address_line_two: Faker::Address.secondary_address,
@@ -46,7 +50,7 @@
 
     item_count = (1..3).to_a.sample
     Product.all.sample(item_count).each do |product|
-      LineItem.create(
+      LineItem.create!(
         order: order,
         product: product,
         unit_price: product.price,