diff --git a/tests/test_utils.py b/tests/test_utils.py
index d8936090..66f8b1ee 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,4 +1,5 @@
 import json
+
 from utils import make_fake_message
 
 
@@ -9,10 +10,10 @@ def test_dataclass_encoder():
     ms = MessageSegment.node_custom(
         "1234", "testtest", "test" + MessageSegment.image("url")
     )
-    s = json.dumps(ms, cls = DataclassEncoder)
+    s = json.dumps(ms, cls=DataclassEncoder)
     assert (
         s
         == '{"type": "node", "data": {"user_id": "1234", "nickname": "testtest", "content": [{"type": "text", "data": {"text": "test"}}, {"type": "image", "data": {"url": "url"}}]}}'
     )
-    s1 = json.dumps("123", cls = DataclassEncoder)
-    assert s1 == '"123"'
\ No newline at end of file
+    s1 = json.dumps("123", cls=DataclassEncoder)
+    assert s1 == '"123"'