old_contents: import unittest
  
  from calexicon.dates import BCEDate
  
  
  class TestBCEDate(unittest.TestCase):
  
      def test_make_bce_date(self):
          bd = BCEDate(-4713, 1, 1)
          self.assertEqual(bd.julian_representation(), (-4713, 1, 1))
  
      def test_equality(self):
          self.assertEqual(BCEDate(-44, 3, 15), BCEDate(-44, 3, 15))
  
new_contents: import unittest
  
  from datetime import timedelta
  
  from calexicon.dates import BCEDate
  
  
  class TestBCEDate(unittest.TestCase):
  
      def test_make_bce_date(self):
          bd = BCEDate(-4713, 1, 1)
          self.assertEqual(bd.julian_representation(), (-4713, 1, 1))
  
      def test_equality(self):
          self.assertEqual(BCEDate(-44, 3, 15), BCEDate(-44, 3, 15))
  
      def test_subtraction(self):
          self.assertEqual(timedelta(days=4), BCEDate(-44, 3, 15) - BCEDate(-44, 3, 11))
          self.assertEqual(timedelta(days=33), BCEDate(-44, 3, 15) - BCEDate(-44, 2, 11))
  
subject: Add tests for the subtraction operator for BCEDate.