diff --git a/python_tests/test_serializers.py b/python_tests/test_serializers.py
index 12181538..c8ffe8c7 100644
--- a/python_tests/test_serializers.py
+++ b/python_tests/test_serializers.py
@@ -1,8 +1,11 @@
 from __future__ import annotations
 
-from unittest import TestCase
-
+import optuna
 from optuna_dashboard._serializer import serialize_attrs
+from optuna_dashboard._serializer import serialize_study_detail
+from optuna_dashboard.preferential import create_study
+
+from optuna_dashboard._storage import get_study_summaries
 
 
 def test_serialize_bytes() -> None:
@@ -17,3 +20,25 @@ def test_serialize_dict() -> None:
         }
     )
     assert len(serialized) <= 1
+
+
+def test_get_study_detail_is_preferential() -> None:
+    storage = optuna.storages.InMemoryStorage()
+    study = create_study(storage=storage)
+    study_summaries = get_study_summaries(storage)
+    assert len(study_summaries) == 1
+
+    study_summary = study_summaries[0]
+    study_detail = serialize_study_detail(study_summary, [], study.trials, [], [], [], False)
+    assert study_detail["is_preferential"]
+
+
+def test_get_study_detail_is_not_preferential() -> None:
+    storage = optuna.storages.InMemoryStorage()
+    study = optuna.create_study(storage=storage)
+    study_summaries = get_study_summaries(storage)
+    assert len(study_summaries) == 1
+
+    study_summary = study_summaries[0]
+    study_detail = serialize_study_detail(study_summary, [], study.trials, [], [], [], False)
+    assert not study_detail["is_preferential"]