api guidelines: adds Test::Unit and RSpec as examples of correct spelling,...

api guidelines: adds Test::Unit and RSpec as examples of correct spelling, also advice when in doubt

railties/guides/source/api_documentation_guidelines.textile

@@ -29,7 +29,9 @@ Documentation has to be concise but comprehensive. Explore and document edge cas
 
 The proper names of Rails components have a space in between the words, like "Active Support". +ActiveRecord+ is a Ruby module, whereas Active Record is an ORM. Historically there has been lack of consistency regarding this, but we checked with David when docrails started. All Rails documentation consistently refer to Rails components by their proper name, and if in your next blog post or presentation you remember this tidbit and take it into account that'd be fenomenal :).
 
-Spell names correctly: Arel, HTML, MySQL, JavaScript, ERb. Use the article "an" for "SQL", as in "an SQL statement". Also "an SQLite database".
+Spell names correctly: Arel, Test::Unit, RSpec, HTML, MySQL, JavaScript, ERb. When in doubt, please have a look at some authoritative source like their official documentation.
+
+Use the article "an" for "SQL", as in "an SQL statement". Also "an SQLite database".
 
 h3. Example Code