A bug report script to reproduce issue #17119 in rails/rails

reproduce_rails_issue_17119.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    gem 'rack', github: 'rack/rack'
    gem 'i18n', github: 'svenfuchs/i18n'
    gem 'sqlite3'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

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

# 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 :posts do |t|
  end

  create_table :authors do |t|
  end
  
  create_table :authors_posts do |t|
    t.integer :author_id
    t.integer :post_id
  end
end

class Author < ActiveRecord::Base
end

class Post < ActiveRecord::Base
  has_and_belongs_to_many :writers, class_name: "Author"
end

class BugTest < Minitest::Test
  def test_habtm_reflections_with_nonstandard_name_and_class_name_option_work_correctly
    post = Post.create!
    post.writers << Author.create!

    # proof that it works at the macro level of using the association
    assert_equal 1, post.writers.count
    
    # proof that it does not work when using reflections API, as Fixtures do
    Post._reflections.values.each do |association|
      assert Kernel.const_defined?(association.class_name), "'#{association.class_name}' expected to be a defined constant, but was not."
    end
  end
end