https://github.com/rails/rails/issues/22723

ActiveRecord 4.1.x to 4.2.x regression issue

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', github: 'rails/rails'
  gem 'arel', github: 'rails/arel'
  gem 'rack', github: 'rack/rack'
  gem 'sprockets', github: 'rails/sprockets'
  gem 'sprockets-rails', github: 'rails/sprockets-rails'
  gem 'sass-rails', github: 'rails/sass-rails'
  gem 'sqlite3'
end

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 :employees, force: true  do |t|
      t.string :first_name
      t.string :last_name
      t.boolean :enabled
  end

  create_table :employee_roles, force: true  do |t|
    t.integer :employee_id
    t.integer :role_id
    t.boolean :enabled
  end

  create_table :roles, force: true  do |t|
      t.string :name
      t.boolean :enabled
  end

  create_table :related_employees, force: true do |t|
    t.boolean :enabled
    t.integer :employee_id
    t.integer :related_employee_id
  end
end

class Employee < ActiveRecord::Base
  default_scope { where(enabled: true) }

  has_many :roles, through: :employee_roles
  has_many :employee_roles

  has_many :related_employees,
           primary_key: :id,
           foreign_key: :employee_id
  has_many :subordinates,
           through: :related_employees,
           source: :employee
end

class RelatedEmployee < ActiveRecord::Base
  default_scope { where(enabled: true) }

  belongs_to :employee,
             primary_key: :id,
             foreign_key: :related_employee_id
end

class Role < ActiveRecord::Base
  default_scope { where(enabled: true) }

  has_many :employees, through: :employee_roles
  has_many :employee_roles

  has_many :subordinates, through: :employees
end

class EmployeeRole < ActiveRecord::Base
      default_scope { where(enabled: true) }

      belongs_to :employee
      belongs_to :role
    end

class BugTest < Minitest::Test
  def test_association_stuff
    employee = Employee.create!(first_name: 'Peter',   last_name: 'Parker', enabled: true)
    employee_2 = Employee.create!(first_name: 'John',   last_name: 'Parker', enabled: true)
    role = Role.create!(name: 'Admin Role', enabled: true)
    EmployeeRole.create!(employee_id: Employee.first.id, role_id: Role.first.id, enabled: true)
    RelatedEmployee.create!(employee_id: Employee.first.id, related_employee_id: Employee.last.id, enabled: true)
    
    assert_equal Role.first.subordinates.first.id, employee_2.id
  end
end