feat(test): Change how to declare test

test/test_owl2yams.py

 import unittest
 import pathlib
 from rdflib import Graph
+from typing import Optional
 from owl2yams import owl_model_to_yams
 from yams.serialize import serialize_to_python
 
@@ -8,11 +9,12 @@
 
 
 class Owl2YamsTC(unittest.TestCase):
-    def test_transform_owl_to_yams(self):
-        data_input = TEST_DATA / "model.owl"
-        expected_output = TEST_DATA / "expected_schema.yams"
+    def _load_owl_and_yams(
+        self, owl_model_file_name: str, yams_schema_file_name: Optional[str] = None
+    ):
+        data_input = TEST_DATA / owl_model_file_name
         owl_model = Graph()
         owl_model.parse(str(data_input), format="turtle")
 
         schema = owl_model_to_yams(owl_model, "TEST")
 
@@ -14,11 +16,17 @@
         owl_model = Graph()
         owl_model.parse(str(data_input), format="turtle")
 
         schema = owl_model_to_yams(owl_model, "TEST")
 
-        with open(expected_output) as f:
-            expected_yams_schema = f.read()
-        self.assertEquals(serialize_to_python(schema), expected_yams_schema)
+        if yams_schema_file_name is not None:
+            expected_output = TEST_DATA / yams_schema_file_name
+            with open(expected_output) as f:
+                expected_yams_schema = f.read()
+            self.assertEquals(serialize_to_python(schema), expected_yams_schema)
+        return schema
+
+    def test_transform_owl_to_yams(self):
+        self._load_owl_and_yams("model.owl", "expected_schema.yams")
 
 
 if __name__ == "__main__":