stop test resetting global state

activerecord/test/cases/yaml_serialization_test.rb

@@ -5,10 +5,16 @@ class YamlSerializationTest < ActiveRecord::TestCase
   fixtures :topics
 
   def test_to_yaml_with_time_with_zone_should_not_raise_exception
+    tz = Time.zone
     Time.zone = ActiveSupport::TimeZone["Pacific Time (US & Canada)"]
     ActiveRecord::Base.time_zone_aware_attributes = true
+
     topic = Topic.new(:written_on => DateTime.now)
     assert_nothing_raised { topic.to_yaml }
+
+  ensure
+    Time.zone = tz
+    ActiveRecord::Base.time_zone_aware_attributes = false
   end
 
   def test_roundtrip