cookies testing

I'm trying to read the expiration time of a cookie for testing, and I'm puzzled because in this functional test both assertion pass ...

   def test_authentication_with_cookie      post :login, :username => 'foo', :password => 'passwd', :remember_me => '1'      assert_not_nil user = User.find(:first, session[:user_id])      assert_equal cookies[:auth_token], user.remember_token      assert_equal cookies[:auth_token], user.remember_token_expiration    end

Someone has a clue of what's happening here ? ...

   ngw