has_one_duplicate.rb

has_one_duplicate.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"
  gem "activerecord", "6.1"
  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 :suppliers do |t|
    t.timestamps
  end

  create_table :accounts do |t|
    t.belongs_to :supplier # no unique index allows for duplicates to be created!
    # t.belongs_to :supplier, index: { unique: true }, foreign_key: true # prevents duplicates
    t.timestamps
  end
end

class Supplier <ActiveRecord::Base
  # we want a 1<->1 association - so that supplier always has one account
  has_one :account
  has_one :account_with_forced_order_asc, -> { order('id asc') }, foreign_key: :supplier_id, class_name: 'Account'
  has_one :account_with_forced_order_desc, -> { order('id desc') }, foreign_key: :supplier_id, class_name: 'Account'
end

class Account <ActiveRecord::Base
  belongs_to :supplier
end

class HasOneTest < Minitest::Test
  def setup
    Account.destroy_all
    Supplier.destroy_all
  end

  def test_has_one_using_association_method
    supplier = Supplier.create!

    supplier.create_account!
    supplier.create_account!

    assert_equal 1, Account.where(supplier: supplier).count # will succeed
    # assert_equal 1, Account.count # (but leave orphaned record if no dependent action bahavior defined - separate issue)
  end

  def test_has_one_duplicate
    supplier = Supplier.create!

    # we are creating 2 accounts for the same supplier (!) although we expect only one
    Account.create!(supplier: supplier)
    Account.create!(supplier: supplier)

    assert_equal 1, Account.where(supplier: supplier).count # will fail - we have a duplicate!
  end

  def test_has_one_duplicate_unordered
    supplier = Supplier.create!

    # we are creating 2 accounts for the same supplier (!) although we expect only one
    account = Account.create!(supplier: supplier)
    Account.create!(supplier: supplier) # duplicate

    assert_equal true, supplier.account == account # flaky - will randomly fail depending on the DB records order
  end

  def test_has_one_duplicate_order_asc
    supplier = Supplier.create!

    # we are creating 2 accounts for the same supplier (!) although we expect only one
    account = Account.create!(supplier: supplier)
    Account.create!(supplier: supplier) # duplicate

    assert_equal true, supplier.account_with_forced_order_asc == account # will fail
  end

  def test_has_one_duplicate_order_desc
    supplier = Supplier.create!

    # we are creating 2 accounts for the same supplier (!) although we expect only one
    account = Account.create!(supplier: supplier)
    Account.create!(supplier: supplier) # duplicate

    assert_equal true, supplier.account_with_forced_order_desc == account # will fail
  end
end