new_contents: from datetime import timedelta
  from unittest import TestCase
  import warnings
  
  from featureforge.experimentation.stats_manager import StatsManager
  
  DEPRECATION_MSG = (
      'Init arguments will change position. '
      'Take a look to http://feature-forge.readthedocs.io/en/latest/experimentation.html'
      '#exploring-the-finished-experiments'
  )
  
  
  class TestStatsManager(TestCase):
  
      def setUp(self):
          self.db_name = 'a_db_name'
  
      def test_init_with_db_name_as_first_parameter_and_booking_duration_as_second(self):
          booking_duration = 10
          st = StatsManager(db_name=self.db_name, booking_duration=booking_duration)
          self.assertEqual(st._db_config['name'], self.db_name)
          self.assertEqual(st.booking_delta, timedelta(seconds=booking_duration))
  
      def test_if_init_with_db_name_as_second_argument_will_warning(self):
          booking_duration = 10
          with self.assertWarns(DeprecationWarning, msg=DEPRECATION_MSG):
              # Trigger a warning.
              StatsManager(booking_duration, self.db_name)
  
      def test_if_use_db_name_as_second_argument_warnings_but_can_continue(self):
          booking_duration = 10
          with self.assertWarns(DeprecationWarning, msg=DEPRECATION_MSG):
              st = StatsManager(booking_duration, self.db_name)
              self.assertEqual(st._db_config['name'], self.db_name)
              self.assertEqual(st.booking_delta, timedelta(seconds=booking_duration))
  
subject: Add a few tests