association_callback.rb

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

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rails', '~> 5.2.0' # Works with '~> 5.1.0'
  gem 'sqlite3'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

puts "Using ActiveRecord #{ActiveRecord::VERSION::STRING}"

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

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

# Schema
ActiveRecord::Schema.define do
  ActiveRecord::Base.connection.create_table(:blogs) do |t|
  end

  ActiveRecord::Base.connection.create_table(:posts) do |t|
    t.integer :blog_id
  end
end

# Models
class Blog < ActiveRecord::Base
  has_many :posts
end

class Post < ActiveRecord::Base
  belongs_to :blog

  after_destroy do
    association(:blog).target = blog
  end
end

class BugTest < Minitest::Test

  def test_bug
    blog = Blog.create!
    post = blog.posts.create!

    post.reload
    post.destroy!
  end

end