1 files changed, 20 insertions, 7 deletions
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index 4fc7e77786..b4e43bdfbc 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -201,6 +201,20 @@ class DirtyTest < ActiveRecord::TestCase
     end
   end
 
+  def test_nullable_datetime_not_marked_as_changed_if_new_value_is_blank
+    in_time_zone 'Edinburgh' do
+      target = Class.new(ActiveRecord::Base)
+      target.table_name = 'topics'
+
+      topic = target.create
+      assert_equal nil, topic.written_on
+
+      topic.written_on = ""
+      assert_equal nil, topic.written_on
+      assert !topic.written_on_changed?
+    end
+  end
+
   def test_integer_zero_to_string_zero_not_marked_as_changed
     pirate = Pirate.new
     pirate.parrot_id = 0
@@ -535,18 +549,17 @@ class DirtyTest < ActiveRecord::TestCase
     end
   end
 
-  def test_setting_time_attributes_with_time_zone_field_to_same_time_should_not_be_marked_as_a_change
+  def test_datetime_attribute_can_be_updated_with_fractional_seconds
     in_time_zone 'Paris' do
       target = Class.new(ActiveRecord::Base)
-      target.table_name = 'pirates'
+      target.table_name = 'topics'
 
-      created_on = Time.now
+      written_on = Time.utc(2012, 12, 1, 12, 0, 0).in_time_zone('Paris')
 
-      pirate = target.create(:created_on => created_on)
-      pirate.reload # Here mysql truncate the usec value to 0
+      topic = target.create(:written_on => written_on)
+      topic.written_on += 0.3
 
-      pirate.created_on = created_on
-      assert !pirate.created_on_changed?
+      assert topic.written_on_changed?, 'Fractional second update not detected'
     end
   end