text: import pytest
  import musdb.audio_classes as ac
  import musdb
  import numpy as np
  
  
  @pytest.fixture(params=[True, False])
  def mus(request):
      return musdb.DB(root='data/MUS-STEMS-SAMPLE', is_wav=request.param)
  
  
  @pytest.fixture(params=[0, 1, 2, 11.1, None])
  def chunk_duration(request):
      return request.param
  
  
  @pytest.fixture(params=[44100.0, 22050.0, 16000.0])
  def sample_rate(request):
      return request.param
  
  
  def test_targets(mus):
      for track in mus:
          for key, target in list(track.targets.items()):
              assert target.audio.shape
  
  
  def test_rates(mus):
      for track in mus:
          assert track.rate == 44100
          assert track.audio.shape
          for key, source in list(track.sources.items()):
              assert source.rate == 44100
              assert source.audio.shape
  
  
  def test_durations(mus):
      for track in mus:
          assert track.duration > 0
          # check if duration is with zero pad range of mp4 files
          # (one frame is typically 1024 samples)
          assert track.audio.shape[0] > (track.duration * track.rate - 1024) \
              and track.audio.shape[0] < (track.duration * track.rate + 1024)
  
  
  def test_sample_rate(mus, sample_rate):
      track = mus[0]
      track.sample_rate = sample_rate
      track.chunk_duration = 1.0
      assert track.audio.shape[0] == sample_rate
  
  
  def test_chunking(mus, chunk_duration):
      for track in mus:
          track.chunk_duration = chunk_duration
          if chunk_duration:
              assert np.allclose(
                  track.audio.shape[0], chunk_duration * track.rate)
              for _, target in track.sources.items():
                  assert np.allclose(
                      target.audio.shape[0], chunk_duration * track.rate)
              for _, target in track.targets.items():
                  assert np.allclose(
                      target.audio.shape[0], chunk_duration * track.rate)
  
  
  def test_track_artisttitle(mus):
      track = ac.MultiTrack(name="None", path="None")
  
      assert track.artist is None
      assert track.title is None
  
  
  def test_source(mus):
      mtrack = ac.MultiTrack(name="abc123", path="None")
      with pytest.raises(ValueError):
          source = ac.Source(mtrack, name="test", path="None")
          source.audio
  
      source.audio = np.zeros((2, 44100))
      assert source.audio.shape == (2, 44100)
  
  
  def test_track(mus):
      with pytest.raises(ValueError):
          track = ac.Track(path="None")
          track.audio
  
      track.audio = np.zeros((2, 44100))
      assert track.audio.shape == (2, 44100)
  