To help understanding ActiveRecord::Rollback

how-ativerecord-rollback-act.rb

# frozen_string_literal: true

require "bundler/inline"

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

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "activerecord"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :articles, force: true do |t|
    t.bigint :category_id
    t.string :title, null: false
    t.text :content, null: false
  end

  create_table :categories, force: true do |t|
    t.string :name, null: false
  end
end

class Article < ActiveRecord::Base
  belongs_to :category
end

class Category < ActiveRecord::Base
  has_many :articles
end

class TestSingleTransaction < MiniTest::Unit::TestCase
  def setup
    Article.delete_all
    Category.delete_all
  end

  def test_use_active_record_rollback
    returned_value = create_and_rollback_by(ActiveRecord::Rollback)
    assert_equal "passed", returned_value
    assert_equal 0, Category.all.count
    assert_equal 0, Article.all.count
  end

  def test_use_runtime_error
    assert_raises RuntimeError do
      create_and_rollback_by(RuntimeError)
    end
    assert_equal 0, Category.all.count
    assert_equal 0, Article.all.count
  end

  private

  def create_and_rollback_by(error)
    ActiveRecord::Base.transaction do
      category = Category.create!(name: 'test')
      Article.create!(category: category, title: 'test', content: 'test')

      raise error, 'raised'
    end

    return 'passed'
  end
end

class TestNestedTransaction < MiniTest::Unit::TestCase
  def setup
    Article.delete_all
    Category.delete_all
  end

  def test_use_active_record_rollback_for_nested_transaction
    returned_value = nested_create_and_rollback_by(ActiveRecord::Rollback)
    assert_equal "passed", returned_value
    assert_equal 1, Category.all.count
    assert_equal 1, Article.all.count
  end

  def test_use_runtime_error_for_nested_transaction
    assert_raises RuntimeError do
      nested_create_and_rollback_by(RuntimeError)
    end
    assert_equal 0, Category.all.count
    assert_equal 0, Article.all.count
  end

  private
  def nested_create_and_rollback_by(error)
    Category.transaction do
      category = Category.create!(name: 'test')

      Article.transaction do
        Article.create!(category: category, title: 'test', content: 'test')
        raise error, 'raised'
      end
    end

    return 'passed'
  end
end

class TestNestedTransactionWithOption < MiniTest::Unit::TestCase
  def setup
    Article.delete_all
    Category.delete_all
  end

  def test_use_active_record_rollback_for_nested_transaction
    returned_value = nested_create_and_rollback_by(ActiveRecord::Rollback)
    assert_equal "passed", returned_value
    assert_equal 1, Category.all.count
    assert_equal 0, Article.all.count
  end

  def test_use_runtime_error_for_nested_transaction
    assert_raises RuntimeError do
      nested_create_and_rollback_by(RuntimeError)
    end
    assert_equal 0, Category.all.count
    assert_equal 0, Article.all.count
  end

  private
  def nested_create_and_rollback_by(error)
    Category.transaction(joinable: false, requires_new: true) do
      category = Category.create!(name: 'test')

      Article.transaction do
        Article.create!(category: category, title: 'test', content: 'test')
        raise error, 'raised'
      end
    end

    return 'passed'
  end
end