new_contents: import unittest
  
  from lessons.lesson_4_temperature import temperature
  
  
  class CtoFTestCase(unittest.TestCase):
      def test_handles_freezing_point(self):
          freezing = temperature.c_to_f(0)
          self.assertEqual(freezing, 32)
  
      def test_handles_boiling_point(self):
          boiling = temperature.c_to_f(100)
          self.assertEqual(boiling, 212)
  
      def test_handle_room_temp(self):
          arbitrary = temperature.c_to_f(20)
          self.assertEqual(arbitrary, 68)
  
      def test_handles_body_temp(self):
          body_temp = temperature.c_to_f(37)
          self.assertEqual(body_temp, 98)
  
  
  class FtoCTestCase(unittest.TestCase):
      def test_handles_freezing_point(self):
          freezing = temperature.f_to_c(32)
          self.assertEqual(freezing, 0)
  
      def test_handles_boiling_point(self):
          boiling = temperature.f_to_c(212)
          self.assertEqual(boiling, 100)
  
      def test_handles_arbitrary_temp(self):
          arbitrary = temperature.f_to_c(68)
          self.assertEqual(arbitrary, 20)
  
      def test_handles_body_temp(self):
          body_temp = temperature.f_to_c(98.6)
          self.assertEqual(body_temp, 37)
  
subject: Add tests for temperature conversions in lesson 4.