How do you test a module that extends ActiveSupport::Concern?

I have a module that extends ActiveSupport::Concern. Here is the `included` block:

    included do       after_save :save_tags

      has_many :taggings, :as => :taggable       has_many :tags, :through => :taggings     end

How can I stub out these calls? I have tried a few ways, but Ruby complains that these methods don't exist when I try and test the module in isolation.