You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: usps_returns_test.rb
    path of file: ./repos/workarea/core/vendor/active_shipping/test/unit/carriers
    
    the code of the file until where you have to start completion: require 'test_helper'

class USPSReturnsTest < ActiveSupport::TestCase
  include ActiveShipping::Test::Fixtures

  attr_reader :carrier

 
    
  def test_parse_external_return_label_response_returns_object
    response = xml_fixture('usps_returns/external_return_label_response')

    assert_equal @carrier.send(:parse_external_return_label_response, response).is_a?(ExternalReturnLabelResponse), true
    assert_equal @carrier.send(:parse_external_return_label_response, response).tracking_number, "9202090140694100000410"
    assert_equal @carrier.send(:parse_external_return_label_response, response).postal_routing, "420770739921"
  end