如何测试依赖Desive signed_in的Rails 5帮助程序?助手,用迷你测试?

给定以下Rails 5帮助器方法,它依赖于Desive帮助器 signed_in?

module ApplicationHelper
  def sign_in_or_out_link
    if signed_in?
      link_to 'Sign Out', destroy_user_session_path, method: :delete
    else
      link_to 'Sign In', new_user_session_path
    end
  end
end

以及希望测试助手是否基于用户的登录状态返回特定链接:

require 'test_helper'

class ApplicationHelperTest < ActionView::TestCase
  test 'returns Sign Out when signed in' do
    assert_match 'Sign Out', sign_in_or_out_link
  end

  test 'returns Sign In when not signed in' do
    assert_match 'Sign In', sign_in_or_out_link
  end
end

测试运行程序引发错误: NoMethodError: undefined method 'signed_in?' for #<ApplicationHelperTest:...> .

虽然我们可以在测试中存根该方法:

class ApplicationHelperTest < ActionView::TestCase

  def signed_in?
    true
  end
  # ..

你签到了吗? 方法,使其返回 false 第二次测试?