Add failing test for lists as additional properties

Author: jyggen

tests/unit/unmarshalling/test_unmarshal.py

@@ -816,3 +816,16 @@ def test_write_only_properties_invalid(self, unmarshaller_factory):
             unmarshaller_factory(spec, context=UnmarshalContext.RESPONSE)(
                 {"id": 10}
             )
+
+    def test_additional_properties_list(self, unmarshaller_factory):
+        schema = {
+            "type": "object"
+        }
+        spec = Spec.from_dict(schema)
+
+        result = unmarshaller_factory(spec, context=UnmarshalContext.RESPONSE)(
+            {"user_ids": [1, 2, 3, 4]}
+        )
+
+        assert is_dataclass(result)
+        assert result.user_ids == [1, 2, 3, 4]