new_contents: from django.test import TestCase
  
  from django.db import models
  from automatic_timestamps.models import TimestampModel
  
  from time import sleep
  
  
  class GenericTimestampTestModel(TimestampModel):
      """A generic, boring model to test timestamp creation against."""
      pass
  
  class TimestampModelTest(TestCase):
      def test_timestamps_are_saved_automatically(self):
          """Test that timestamps are set when a model is saved."""
          model = GenericTimestampTestModel()
          model.save()
          
          self.assertTrue(model.created_at)
          self.assertTrue(model.updated_at)
      
      def test_timestamp_is_updated(self):
          """Test that the updated_at field is set on save()."""
          model = GenericTimestampTestModel()
          model.save()
          
          last_time_saved = model.updated_at
          
          sleep(1)
          
          model.save()
          
          self.assertNotEqual(last_time_saved, model.updated_at)
      
      def test_created_timestamp_is_not_updated(self):
          """Test that the created_at field is not changed on subsequent saves."""
          model = GenericTimestampTestModel()
          model.save()
          
          created = model.created_at
          
          sleep(1)
          
          model.save()
          
          self.assertEqual(created, model.created_at)
          
subject: Add unit tests to the automatic_timestamps module