text: from unittest import TestCase
  
  from aiortc import RTCSessionDescription
  
  
  class RTCSessionDescriptionTest(TestCase):
      def test_bad_type(self):
          with self.assertRaises(ValueError) as cm:
              RTCSessionDescription(sdp='v=0\r\n', type='bogus')
          self.assertEqual(
              str(cm.exception),
              "'type' must be in ['offer', 'pranswer', 'answer', 'rollback'] (got 'bogus')")
  
      def test_good_type(self):
          desc = RTCSessionDescription(sdp='v=0\r\n', type='answer')
          self.assertEqual(desc.sdp, 'v=0\r\n')
          self.assertEqual(desc.type, 'answer')
  