I'm trying to understand Active Record again....

migration_create_user.rb

class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
      t.string      :email
      t.string      :first_name
      t.string      :last_name     
      t.timestamps
    end

    add_index :users, :email, unique: true
  end
end

user.rb

# http://api.rubyonrails.org/classes/ActiveModel/Validations/ClassMethods.html
class User < ActiveRecord::Base
  validates :first_name,  presence: true
  validates :last_name,   presence: true 
  validates :email,       presence: true, uniqueness: true, format:{ with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i}
end

user_test.rb

require 'test_helper'

#http://guides.rubyonrails.org/active_record_querying.html
class UserTest < ActiveSupport::TestCase
  def setup
    @user_fields = {first_name: 'Chris', last_name: 'S', email: 'cs@foo.com'}
  end

  test "it should validate with all fields present" do
    user = User.new(@user_fields)
    assert user.valid?, 'Expect user to be valid'
  end

  test "it should require email to be unique" do
    user = User.new(@user_fields)
    user.save
    assert_equal 1, User.count

    user = User.new(@user_fields.merge(first_name: 'John', last_name: 'Smith'))
    assert !user.valid?, 'Expect second user to be invalid'
    assert_raises(ActiveRecord::RecordInvalid) do
      user.save!
    end
    assert_equal 1, User.count
  end

  # this really isn't a good test, but i want to make sure i understand Active Record finders still
  test "it should find by last_name" do
    User.new(@user_fields).save!
    assert 1, User.count

    # find with new find_by
    user = User.find_by first_name: 'Chris'
    assert user.instance_of?(User), 'Expect user to be of type User'
    assert_equal 'cs@foo.com', user.email, 'Expect email to be cs@foo.com'

    # find with where
    users = User.where('first_name = ?', 'Chris').order(:first_name)
    assert users, 'Expect a users array'
    assert_equal 1, users.size, 'Expect only 1 user'
    assert_equal 'cs@foo.com', users.first.email, 'Expect email to be cs@foo.com'
  end

  # meta-test that all user fields must be present
  [:first_name, :last_name, :email].each do |field|
    test "it should require #{field} to be present" do
      @user_fields.delete(field)
      user = User.new(@user_fields)
      assert !user.valid?, 'Expect user to be invalid'
      assert user.errors[field], "Expect #{field} to have validation errors"
    end
  end

  test "it should require a valid email" do
    user = User.new(@user_fields)
    user.email = 'i am not an email'
    assert !user.valid?, 'Expect user to be invalid'
    assert user.errors[:email], 'Expect email to have validation errors'
  end
end