binding_test.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 'activerecord', '4.2.4'
  gem 'sqlite3'
  gem 'pg'
end

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

Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

database_configuration = {
  adapter: 'postgresql',
  database: 'rails_issues',
  username: 'konstantin',
  password: 'postgres',
  host: 'localhost'
}

adapter_tasker = ActiveRecord::Tasks::PostgreSQLDatabaseTasks.new(database_configuration.stringify_keys)
adapter_tasker.drop
adapter_tasker.create

ActiveRecord::Schema.define do
  create_table :users do |t|
    t.string :status
    t.string :gender
  end
end

class User < ActiveRecord::Base
  scope :active, -> { where(status: :active) }
  scope :male,   -> { where(gender: :male)   }

  def self.custom_arel_scope
    # Compose two scopes and JOIN with OR
    where(active.male.where_values.reduce(:or))
  end
end

class BugTest < Minitest::Test
  def test_pg_binding
     assert User.custom_arel_scope.to_a
  end
end