In Rails how do I test modifications to an instance of a Model that are made in a controller?

Question

I'm just getting my feet wet in writing a testing suite for my Rails application. I'm using Factory Girl and Shoulda on a Rails 3 app. In my controller I have:

def create
@topic = @forum.topics.build(params[:topic])
@topic.user = current_user

#So the topic gets pushed to the top without any replies
@topic.last_poster = current_user
@topic.last_post_at = Time.now

respond_to do |format|
  if @topic.save
    format.html { redirect_to(forum_topic_path(@topic.forum, @topic), :notice => 'Topic was successfully created.') }
    format.xml  { render :xml => @topic, :status => :created, :location => @topic }
  else
    format.html { render :action => "new" }
    format.xml  { render :xml => @topic.errors, :status => :unprocessable_entity }
  end
end
end

My question is how would I write test verifying that @topic.last_post_at gets timestamped and saved correctly and would I write this test as a functional test or a unit test?

Answer 1

Firstly, I would move a lot of this functionality into the model. For example:

class Topic
  after_create :set_defaults

  protected

  def set_defaults
    update_attributes :last_poster => self.user, :last_post_at => Time.now
  end
end

I would then write a model test to make sure that the Time and user get set and simplify my controller code like this:

def create
  @topic = @forum.topics.build(params[:topic].merge({:user => current_user}))

  respond_to do |format|
    ...
  end
end