Raising ActiveRecord::Rollback

I had a bit of code that I was running in a transaction block. Like so:

ActiveRecord::Base.transaction do
  @rating = Rating.new(rater: @user, rateable: @movie, score: params[:score])
  if !@rating.save
    Rails.logger.error("Error saving rating")
    raise ActiveRecord::Rollback

I kept trying to test this by doing:

expect { post :create etc }.to raise_error ActiveRecord::Rollback

Total failure. Couldn’t figure out why for a while. Here’s the reason: raising ActiveRecord::Rollback just triggers a rollback of the transaction and does so silently. What I should’ve done is raise a different type of error (TBD) and that will still trigger a rollback of the transaction but the error will actually be raised and we can return an appropriate page to the user.

More info on StackOverflow.