module ActiveRecord::TestFixtures

def setup_fixtures(config = ActiveRecord::Base)
  if pre_loaded_fixtures && !use_transactional_tests
    raise RuntimeError, "pre_loaded_fixtures requires use_transactional_tests"
  end
  @fixture_cache = {}
  @fixture_connections = []
  @@already_loaded_fixtures ||= {}
  @connection_subscriber = nil
  @legacy_saved_pool_configs = Hash.new { |hash, key| hash[key] = {} }
  @saved_pool_configs = Hash.new { |hash, key| hash[key] = {} }
  # Load fixtures once and begin transaction.
  if run_in_transaction?
    if @@already_loaded_fixtures[self.class]
      @loaded_fixtures = @@already_loaded_fixtures[self.class]
    else
      @loaded_fixtures = load_fixtures(config)
      @@already_loaded_fixtures[self.class] = @loaded_fixtures
    end
    # Begin transactions for connections already established
    @fixture_connections = enlist_fixture_connections
    @fixture_connections.each do |connection|
      connection.begin_transaction joinable: false, _lazy: false
      connection.pool.lock_thread = true if lock_threads
    end
    # When connections are established in the future, begin a transaction too
    @connection_subscriber = ActiveSupport::Notifications.subscribe("!connection.active_record") do |_, _, _, _, payload|
      spec_name = payload[:spec_name] if payload.key?(:spec_name)
      shard = payload[:shard] if payload.key?(:shard)
      setup_shared_connection_pool if ActiveRecord.legacy_connection_handling
      if spec_name
        begin
          connection = ActiveRecord::Base.connection_handler.retrieve_connection(spec_name, shard: shard)
        rescue ConnectionNotEstablished
          connection = nil
        end
        if connection
          setup_shared_connection_pool unless ActiveRecord.legacy_connection_handling
          if !@fixture_connections.include?(connection)
            connection.begin_transaction joinable: false, _lazy: false
            connection.pool.lock_thread = true if lock_threads
            @fixture_connections << connection
          end
        end
      end
    end
  # Load fixtures for every test.
  else
    ActiveRecord::FixtureSet.reset_cache
    @@already_loaded_fixtures[self.class] = nil
    @loaded_fixtures = load_fixtures(config)
  end
  # Instantiate fixtures for every test if requested.
  instantiate_fixtures if use_instantiated_fixtures
end