Is it possible to set when a cookie expires inside an integration test?

Is there a way in integration tests to manipulate a cookie's expiration date (as to test if it is taken into account properly). For example, if cookies['user_id'] already exists in the test, manipulate:

cookies['user_id'].expires = Time.zone.now - 1.day

(this returns undefined method 'expires=')
I'm using MiniTest in Rails.