I could not get these tests to pass either. I got the following errors:

1) Voting system should vote a comment up
     Failure/Error: comment = FactoryGirl.create(:comment)
     ActiveRecord::StatementInvalid:
       Could not find table 'comments'
     # ./spec/features/voting_spec.rb:12:in `block (2 levels) in <top (required)>'

  2) Voting system should vote a comment down
     Failure/Error: comment = FactoryGirl.create(:comment)
     ActiveRecord::StatementInvalid:
       Could not find table 'comments'
     # ./spec/features/voting_spec.rb:47:in `block (2 levels) in <top (required)>'

I see in db/schema.rb there is no mention of the comments table. However, I do see that you created a migration to add the link_id to comments and I see the association to comments in link.rb. Also, I'm able to see the comments table in the Rails console. I'm not sure what the problem is. Perhaps a migration or commit issue?