Rails: How to unit test the formatting of model fields in the views.

In our Rails applications we often use Textile/RedCloth or some other libraries to have things like Post's content nicely formatted in the view. I use acts_as_textiled. This plugin simplifies the code a lot. All that is needed in order to make a certain field 'textilized' is this line:

class Post < ActiveRecord::Base
  acts_as_textiled  :content
end

The question that I want to focus on here is:

How to unit test that a certain field will be nicely formatted in the views?


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As Jay Fields has already explained (he focused on testing validations in his article) there are two approaches:
The first one is based on listing all the cases that are important, like whether paragraph tags are correctly inserted or whether bold tags are correct. It may be sometimes useful but for me it's a code smell that for testing a single line in your codebase you need so many test lines of code. Additionally, the acts_as_textiled plugin is nicely tested/specified so why duplicate the code? I'd rather test some of those cases in my Selenium tests or functional tests and choose the second approach:

  def test_content_is_nicely_formatted
    Post.expects(:acts_as_textiled).with(:content)
    load "#{RAILS_ROOT}/app/models/post.rb"
  end

I'm using mocha here for setting an expectation that a class method called acts_as_textiled will be called (passing the field name argument) during the load time of the class file. This solution is not ideal. I don't like hardcoding the path here but I still find it simpler that the first approach.
This way testing of things like validations and acts_as_* calls becomes much simpler.