Add nested serializer with list tests

TestNestedSerializerWithList checks if a list (a MulitpleChoiceField in
this case) in a nested serializer is correctly parsed from json or
multipart formatted data.

tests/test_serializer_nested.py

@@ -167,3 +167,32 @@ class TestNestedSerializerWithMany:
 
         expected_errors = {'not_allow_empty': {'non_field_errors': [serializers.ListSerializer.default_error_messages['empty']]}}
         assert serializer.errors == expected_errors
+
+
+class TestNestedSerializerWithList:
+    def setup(self):
+        class NestedSerializer(serializers.Serializer):
+            example = serializers.MultipleChoiceField(choices=[1, 2, 3])
+
+        class TestSerializer(serializers.Serializer):
+            nested = NestedSerializer()
+
+        self.Serializer = TestSerializer
+
+    def test_nested_serializer_with_list_json(self):
+        input_data = {
+            'nested': {
+                'example': [1, 2],
+            }
+        }
+        serializer = self.Serializer(data=input_data)
+
+        assert serializer.is_valid()
+        assert serializer.validated_data['nested']['example'] == set([1, 2])
+
+    def test_nested_serializer_with_list_multipart(self):
+        input_data = QueryDict('nested.example=1&nested.example=2')
+        serializer = self.Serializer(data=input_data)
+
+        assert serializer.is_valid()
+        assert serializer.validated_data['nested']['example'] == set([1, 2])