new_contents: import os
  from unittest import TestCase
  
  from aiortc.contrib.media import AudioFileTrack
  
  from .utils import run
  
  
  class FileTrackTest(TestCase):
      def test_audio_file_track(self):
          path = os.path.join(
              os.path.dirname(__file__), os.path.pardir, 'examples', 'server', 'demo-instruct.wav')
          track = AudioFileTrack(path=path)
  
          # read first frame
          frame = run(track.recv())
          self.assertEqual(frame.channels, 1)
          self.assertEqual(len(frame.data), 320)
          self.assertEqual(frame.sample_rate, 8000)
          self.assertEqual(frame.sample_width, 2)
  
          # read another frame
          frame = run(track.recv())
          self.assertEqual(frame.channels, 1)
          self.assertEqual(len(frame.data), 320)
          self.assertEqual(frame.sample_rate, 8000)
          self.assertEqual(frame.sample_width, 2)
  
subject: add a test for AudioFileTrack