problem_to_solve.rb

# frozen_string_literal: true

# Question:
# a = 1
# b = 2
# a ||= b
#
# What is the result?

begin
  require 'bundler/inline'
rescue LoadError => e
  warn 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'

  gem 'activerecord', '~> 7.0'
  gem 'activesupport', '~> 7.0'
  gem 'sqlite3', '1.4'

  gem 'minitest-reporters'
  gem 'minitest-fail-fast'
end

###### Config START
require 'active_record'
require 'minitest/autorun'
require 'minitest/reporters'
require 'minitest/fail_fast'

Minitest::FailFastReporter.fail_fast!
ActiveSupport::TestCase.test_order = :sorted

Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')

###### Config END

##### Migration START
ActiveRecord::Schema.define do
  create_table :users, force: true do |t|
    t.integer :state, default: 0

    t.string :name
    t.text :bio
    t.integer :comments_count, null: false, default: 0
  end

  create_table :comments, force: true do |t|
    t.integer :user_id
    t.string :body
  end

  create_table :user_details, force: true do |t|
    t.integer :user_id
    t.string :bsb
  end

  create_table :images, force: true do |t|
    t.references :imageable, polymorphic: true, index: true
    t.string :url
  end
end
##### Migration END

##### ActiveRecord Models START
class Comment < ActiveRecord::Base
  belongs_to :user
end

class User < ActiveRecord::Base
  include Singleton

  has_many :images
  has_many :comments, counter_cache: true
  has_one :user_detail

  delegate :bsb, to: :user_detail

  def user_detail
    super || create_user_detail
  end
end

class UserDetail < ActiveRecord::Base
end

class Image < ActiveRecord::Base
  belongs_to :imageable, polymorphic: true
end

##### ActiveRecord Models END

############ TEST SUITE ############
class SimpleTest < Minitest::Test
  def setup
    @user = User.create(name: 'Bob', bio: '0' * 100_000)
    @user2 = User.create(name: 'John', bsb: '111-111')

    [*1..20].tap do |i|
      c = @user.comments.find_or_create_by(body: "Hello #{i}")
      c.update!(body: 'Hello again!')
    end

    @user_comments = []

    @sql_requests_counter = perform_sql do
      Comment.find_each do |c|
        @user_comments << { c.body => c.user.name }
      end
    end
  end

  ############### DON'T MODIFY AFTER THIS LINE ###############

  def teardown
    ActiveRecord::Base.subclasses.each(&:delete_all)
  end

  def perform_sql(tick: 0, &block)
    counter_f = ->(*) { tick += 1 }

    ActiveSupport::Notifications.subscribed(counter_f, 'sql.active_record', &block)

    tick
  end

  def test_models
    assert_equal 20, @user.comments_count
    assert_equal 20, @user_comments.count
    assert_includes [1, 2], @sql_requests_counter
  end

  def test_attributes
    @user.update!(bsb: '999-999')

    assert_equal '999-999', @user.bsb
    assert_equal '111-111', @user2.bsb
  end

  def test_relations_polymorphic
    @user.images.create(url: 'https://images.com/1.png')

    assert_equal 1, Image.count
  end

  def test_user_status
    @user.inactive!

    assert_equal false, @user.active?
  end

  def test_destroy_relation
    @user.destroy

    assert_equal 0, Comment.count
  end
end