diff --git a/githubkit/core.py b/githubkit/core.py
index 108f05625..82fbf997f 100644
--- a/githubkit/core.py
+++ b/githubkit/core.py
@@ -4,7 +4,7 @@
 from datetime import datetime, timedelta, timezone
 import time
 from types import TracebackType
-from typing import TYPE_CHECKING, Any, Generic, TypeVar, cast, overload
+from typing import TYPE_CHECKING, Any, Generic, TypeVar, overload
 
 import anyio
 import httpx
diff --git a/tests/test_unit_test/test_unit_test.py b/tests/test_unit_test/test_unit_test.py
index 86892f9bf..455c15831 100644
--- a/tests/test_unit_test/test_unit_test.py
+++ b/tests/test_unit_test/test_unit_test.py
@@ -1,7 +1,7 @@
+from datetime import timedelta
 import json
 from pathlib import Path
 import threading
-from datetime import timedelta
 from typing import Any, TypeVar
 
 from githubkit_schemas.latest.models import FullRepository
@@ -110,6 +110,7 @@ def test_mem_cache_passive_expiry():
     cache.set("key2", "val2", timedelta(hours=1))
 
     import time
+
     time.sleep(0.01)
 
     assert cache.get("key1") is None
@@ -119,10 +120,9 @@ def test_mem_cache_passive_expiry():
 
 def test_core_context_manager_safety():
     gh = GitHubCore()
-    with pytest.raises(RuntimeError):
-        with gh:
-            with gh:
-                pass
+    with gh:
+        with pytest.raises(RuntimeError):
+            gh.__enter__()
 
     # Ensure no lingering client after error
     assert gh._GitHubCore__sync_client.get() is None