Add test for Observer#observer_class and change the implementation slightly. Closes #11099 [ernesto.jimenez]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8875 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/lib/active_record/observer.rb

@@ -151,10 +151,10 @@ module ActiveRecord
       end
 
       # The class observed by default is inferred from the observer's class name:
-      #   assert_equal [Person], PersonObserver.observed_class
+      #   assert_equal Person, PersonObserver.observed_class
       def observed_class
-        if observed_class_name = name.scan(/(.*)Observer/)[0]
-          observed_class_name[0].constantize
+        if observed_class_name = /(.*)Observer/.match(name)[1]
+          observed_class_name.constantize
         else
           nil
         end

activerecord/test/cases/lifecycle_test.rb

@@ -134,4 +134,8 @@ class LifecycleTest < ActiveRecord::TestCase
   def test_invalid_observer
     assert_raise(ArgumentError) { Topic.observers = Object.new; Topic.instantiate_observers }
   end
+
+  def test_getting_observed_class_from_class_name
+    assert_equal Topic, TopicObserver.observed_class
+  end
 end