      title = serializers.CharField(max_length=100)
      duration = serializers.IntegerField()
  
  
  class AlbumSerializer(serializers.Serializer):
      album_name = serializers.CharField(max_length=100)
      artist = serializers.CharField(max_length=100)
      tracks = TrackSerializer(many=True)
  
  
  class NestedSerializerTestCase(TestCase):
      def test_nested_validation_success(self):
          """
 
</s> remove class NestedSerializerTestCase(TestCase):
 </s> add  </s> remove class TrackSerializer(serializers.Serializer):
    order = serializers.IntegerField()
    title = serializers.CharField(max_length=100)
    duration = serializers.IntegerField()
 </s> add class WritableNestedSerializerBasicTests(TestCase):
    """
    Tests for deserializing nested entities.
    Basic tests that use serializers that simply restore to dicts.
    """ </s> remove         serializer = AlbumSerializer(data=data)
 </s> add         serializer = self.AlbumSerializer(data=data)
        class AlbumSerializer(serializers.Serializer):
            album_name = serializers.CharField(max_length=100)
            artist = serializers.CharField(max_length=100)
            tracks = TrackSerializer(many=True)
      title = serializers.CharField(max_length=100)
      duration = serializers.IntegerField()
  
  
        class AlbumSerializer(serializers.Serializer):
            album_name = serializers.CharField(max_length=100)
            artist = serializers.CharField(max_length=100)
            tracks = TrackSerializer(many=True)
        class AlbumSerializer(serializers.Serializer):
            album_name = serializers.CharField(max_length=100)
            artist = serializers.CharField(max_length=100)
            tracks = TrackSerializer(many=True)
        class AlbumSerializer(serializers.Serializer):
            album_name = serializers.CharField(max_length=100)
            artist = serializers.CharField(max_length=100)
            tracks = TrackSerializer(many=True)
        class AlbumSerializer(serializers.Serializer):
            album_name = serializers.CharField(max_length=100)
            artist = serializers.CharField(max_length=100)
            tracks = TrackSerializer(many=True)
  
  
  class NestedSerializerTestCase(TestCase):
      def test_nested_validation_success(self):
          """
keep keep keep keep replace replace replace replace keep keep keep keep keep
 Extra tests for nested serializers 
rest_framework/tests/serializer_nested.py