Test case reproducing an issue that causes a record to be inserted without a require foreign key (foo_id)

rspec has_one build bug

require "bundler/inline"

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

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

  gem "rails", "5.2.2"
  gem "sqlite3", '~> 1.3.13'
  gem "factory_bot", "4.11.1"
end

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


# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :users, force: true do |t|
  end

  create_table :tasks, force: true do |t|
    t.integer :user_id, null: false, index: true
    t.integer :foo_id, null: false, index: true
  end
end

class User < ActiveRecord::Base
  has_one :task
end

class Task < ActiveRecord::Base
  belongs_to :user, dependent: :destroy
  belongs_to :foo, class_name: 'User'
end

FactoryBot.define do
  factory :user do
  end

  factory :task do
    association :user, strategy: :build
    association :foo, factory: :user, strategy: :build
  end
end

class BugTest < Minitest::Test
  def test_factory_bot_stuff
    task = FactoryBot.create(:task)
    assert task.foo_id.present?
  end
end