old_contents: from test_calendar import CalendarTest
  
  from qual.calendars import EnglishHistoricalCalendar
  
  class TestHistoricalCalendar(object):
      def setUp(self):
          self.calendar = self.calendar_type()
  
      def test_before_switch(self):
          for triplet in self.julian_triplets:
              self.check_valid_date(*triplet)
  
      def test_after_switch(self):
          for triplet in self.gregorian_triplets:
              self.check_valid_date(*triplet)
  
      def test_during_switch(self):
          for triplet in self.transition_triplets:
              self.check_invalid_date(*triplet)
  
  class TestEnglishHistoricalCalendar(TestHistoricalCalendar, CalendarTest):
      calendar_type = EnglishHistoricalCalendar
      gregorian_triplets = [(1752, 9, 14)]
      julian_triplets = [(1752, 9, 1), (1752, 9, 2)]
      transition_triplets = [(1752, 9, 3), (1752, 9, 6), (1752, 9, 13)]
  
new_contents: from test_calendar import CalendarTest
  
  from qual.calendars import EnglishHistoricalCalendar
  
  class BaseTestHistoricalCalendar(object):
      def setUp(self):
          self.calendar = self.calendar_type()
  
      def test_before_switch(self):
          for triplet in self.julian_triplets:
              self.check_valid_date(*triplet)
  
      def test_after_switch(self):
          for triplet in self.gregorian_triplets:
              self.check_valid_date(*triplet)
  
      def test_during_switch(self):
          for triplet in self.transition_triplets:
              self.check_invalid_date(*triplet)
  
  class TestEnglishHistoricalCalendar(BaseTestHistoricalCalendar, CalendarTest):
      calendar_type = EnglishHistoricalCalendar
      gregorian_triplets = [(1752, 9, 14)]
      julian_triplets = [(1752, 9, 1), (1752, 9, 2)]
      transition_triplets = [(1752, 9, 3), (1752, 9, 6), (1752, 9, 13)]
  
subject: Rename base class.