json_serializer_test.rb

  class ActionDispatch::Session::JsonSerializer
    def self.load(value)
      JSON.load(value) + " and loaded"
    end

    def self.dump(value)
      JSON.dump(value + " was dumped")
    end
  end

  def test_encrypted_cookie_using_json_serializer
    @request.env["action_dispatch.session_serializer"] = :json_serializer
    get :set_encrypted_cookie
    cookies = @controller.send :cookies
    assert_not_equal 'bar', cookies[:foo]
    assert_raises TypeError do
      cookies.signed[:foo]
    end
    assert_equal 'bar was dumped and loaded', cookies.encrypted[:foo]
  end