Fixed final test. Added .gitignore file.

.gitignore

@@ -0,0 +1,18 @@
+*.gem
+*.rbc
+.bundle
+.config
+.yardoc
+*.swp
+Gemfile.lock
+InstalledFiles
+_yardoc
+coverage
+doc/
+lib/bundler/man
+pkg
+rdoc
+spec/reports
+test/tmp
+test/version_tmp
+tmp

lib/slugtastic/model_additions.rb

@@ -3,8 +3,7 @@ module Slugtastic
 
     def has_slug name, options = { :from => :title }
       before_validation do |record|
-        return if responds_to?(name) and send(name).present?
-        send("#{name}=", Slugtastic.generate_slug(send(options[:from])))
+        send("#{name}=", Slugtastic.generate_slug(send(options[:from]))) if send(name).nil? or send(name).blank?
       end
     end
 

spec/slugtastic/model_additions_spec.rb

@@ -4,6 +4,7 @@ require 'spec_helper'
 class Model < SuperModel::Base
   include ActiveModel::Validations::Callbacks
   extend Slugtastic::ModelAdditions
+  attr_accessor :slug, :title
   has_slug :slug, from: :title
 end