gistfile1.rb

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

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

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

# 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)
  ActiveRecord::Base.connection.create_table(:authors) do |t|
    t.string :name
  end

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

# Models
class Blog < ActiveRecord::Base
  has_many :posts, -> { joins(:author).order('authors.name') }
end

class Post < ActiveRecord::Base
  belongs_to :blog
  belongs_to :author
end

class Author < ActiveRecord::Base
  has_many :posts
end

class BugTest < Minitest::Test
  def setup
    Blog.delete_all
    Post.delete_all
    Author.delete_all
  end

  def test_eager_load_with_join
    blog = Blog.create!
    author = Author.create!
    blog.posts.create!(author: author)
    
    # Make sure it works without eager loading
    assert_equal([author], Blog.all.to_a.flat_map(&:posts).map(&:author).to_a)
    
    # Now try it with eager loading
    assert_equal([author], Blog.includes(:posts).to_a.flat_map(&:posts).map(&:author).to_a)
  end
end