diff --git a/easygraph/tests/test_hif.py b/easygraph/tests/test_hif.py
index a598bdc6..a4c90720 100644
--- a/easygraph/tests/test_hif.py
+++ b/easygraph/tests/test_hif.py
@@ -1,34 +1,32 @@
-import unittest
 import json
-import os
 import tempfile
-import easygraph as eg
+import unittest
+
 from pathlib import Path
 
+import easygraph as eg
+
+
 MOCK_HIF_DATA = {
-    "metadata": {
-        "name": "test_organism",
-        "description": "Simulation for unit test"
-    },
+    "metadata": {"name": "test_organism", "description": "Simulation for unit test"},
     "network-type": "directed",
     "nodes": [
         {"node": "n1", "weight": 1.0, "attrs": {"name": "Node A"}},
-        {"node": "n2", "weight": 1.0, "attrs": {"name": "Node B"}}
-    ],
-    "edges": [
-        {"edge": "e1", "weight": 1.0, "attrs": {"name": "Edge Alpha"}}
+        {"node": "n2", "weight": 1.0, "attrs": {"name": "Node B"}},
     ],
+    "edges": [{"edge": "e1", "weight": 1.0, "attrs": {"name": "Edge Alpha"}}],
     "incidences": [
         {"edge": "e1", "node": "n1", "weight": 1.0, "direction": "tail"},
-        {"edge": "e1", "node": "n2", "weight": 1.0, "direction": "head"}
-    ]
+        {"edge": "e1", "node": "n2", "weight": 1.0, "direction": "head"},
+    ],
 }
 
+
 class HIFTest(unittest.TestCase):
     def setUp(self):
         self.temp_dir = tempfile.TemporaryDirectory()
         self.temp_dir_path = Path(self.temp_dir.name)
-        
+
         self.input_file = self.temp_dir_path / "input_mock.hif.json"
         self.output_file = self.temp_dir_path / "output_result.hif.json"
 
@@ -44,52 +42,76 @@ def test_hif_roundtrip_preservation(self):
         EasyGraph object is structurally valid.
         """
         hg = eg.hif_to_hypergraph(filename=self.input_file)
-       
+
         self.assertEqual(hg.num_v, 2, "Loaded graph should have 2 nodes")
         self.assertEqual(hg.num_e, 1, "Loaded graph should have 1 edge")
-        
-        node_names = [props.get('name') for props in hg.v_property]
-        self.assertIn("n1", node_names, "Node ID 'n1' should be in v_property")
-        
+
+        node_names = [props.get("name") for props in hg.v_property]
+        self.assertEqual(
+            node_names,
+            ["Node A", "Node B"],
+            "HIF attrs.name should be preserved in v_property",
+        )
+
+        hif_node_ids = [node["node"] for node in hg.custom_hif_nodes]
+        self.assertEqual(
+            hif_node_ids,
+            ["n1", "n2"],
+            "Original HIF node IDs should be preserved separately",
+        )
+
         edges = hg.e[0]
         self.assertEqual(len(edges), 1, "Should have 1 edge group")
         self.assertEqual(len(edges[0]), 2, "Edge e1 should connect 2 nodes")
-        
-        self.assertTrue(hasattr(hg, "custom_hif_incidences"), "Failed to attach custom incidences")
+
+        self.assertTrue(
+            hasattr(hg, "custom_hif_incidences"), "Failed to attach custom incidences"
+        )
         self.assertTrue(hasattr(hg, "metadata"), "Failed to attach metadata")
 
         eg.hypergraph_to_hif(hg, filename=self.output_file)
-        
-        with open(self.output_file, 'r', encoding="utf-8") as f:
+
+        with open(self.output_file, "r", encoding="utf-8") as f:
             res = json.load(f)
-            
+
+            output_node_ids = [node["node"] for node in res["nodes"]]
+            self.assertEqual(
+                output_node_ids,
+                ["n1", "n2"],
+                "Original HIF node IDs should survive roundtrip export",
+            )
+
             first_incidence = res["incidences"][0]
-            self.assertIn("direction", first_incidence, "'direction' field lost in roundtrip")
+            self.assertIn(
+                "direction", first_incidence, "'direction' field lost in roundtrip"
+            )
             self.assertIn(first_incidence["direction"], ["tail", "head"])
-            
-            self.assertNotIn("default_attrs", res["metadata"], "'default_attrs' was forced into metadata")
+
+            self.assertNotIn(
+                "default_attrs",
+                res["metadata"],
+                "'default_attrs' was forced into metadata",
+            )
             self.assertEqual(res["metadata"]["name"], "test_organism")
 
     def test_manual_graph_export(self):
         """Test exporting a manually created Hypergraph (not loaded from file)."""
         hg = eg.Hypergraph(
-            num_v=5, 
-            e_list=[(0, 1, 2), (2, 3), (2, 3), (0, 4)], 
-            merge_op="sum"
+            num_v=5, e_list=[(0, 1, 2), (2, 3), (2, 3), (0, 4)], merge_op="sum"
         )
         hg.metadata = {"created_by": "manual_test"}
 
         eg.hypergraph_to_hif(hg, filename=self.output_file)
-        
-        with open(self.output_file, 'r', encoding="utf-8") as f:
+
+        with open(self.output_file, "r", encoding="utf-8") as f:
             data = json.load(f)
             self.assertEqual(len(data["nodes"]), 5)
-            self.assertEqual(len(data["edges"]), 3) 
+            self.assertEqual(len(data["edges"]), 3)
             self.assertEqual(data["metadata"]["created_by"], "manual_test")
-            
 
             weights = [e["weight"] for e in data["edges"]]
             self.assertIn(2.0, weights, "Merged edge weight should be 2.0")
 
+
 if __name__ == "__main__":
-    unittest.main()
\ No newline at end of file
+    unittest.main()