fixed test:units rake task

test/factories/tag.rb

@@ -1,18 +1,18 @@
 Factory.define(:tag) do |f|
   f.name {Faker::Name.first_name.downcase}
   f.post_count 0
-  f.category Tag.categories.general
+  f.category {Tag.categories.general}
   f.related_tags ""
 end
 
 Factory.define(:artist_tag, :parent => :tag) do |f|
-  f.category Tag.categories.artist
+  f.category {Tag.categories.artist}
 end
 
 Factory.define(:copyright_tag, :parent => :tag) do |f|
-  f.category Tag.categories.copyright
+  f.category {Tag.categories.copyright}
 end
 
 Factory.define(:character_tag, :parent => :tag) do |f|
-  f.category Tag.categories.character
+  f.category {Tag.categories.character}
 end