diff --git a/tests/test_gcs.py b/tests/test_gcs.py
index 65a64aa..10580e9 100644
--- a/tests/test_gcs.py
+++ b/tests/test_gcs.py
@@ -1,37 +1,38 @@
 import os
+from unittest.mock import MagicMock
 from unittest.mock import patch
 
 from dapla.gcs import GCSFileSystem
 
 
-@patch('google.auth.default', return_value=(None, None))
-def test_instance(mock_auth) -> None:
+@patch("google.auth.default", return_value=(None, None))
+def test_instance(mock_auth: MagicMock) -> None:
     client = GCSFileSystem()
     assert client is not None
 
 
-@patch('google.auth.default', return_value=(None, None))
-def test_init_with_dapla_lab(mock_auth) -> None:
+@patch("google.auth.default", return_value=(None, None))
+def test_init_with_dapla_lab(mock_auth: MagicMock) -> None:
     os.environ["DAPLA_REGION"] = "dapla-lab"
     client = GCSFileSystem(project="test-project")
     assert client is not None
 
 
-@patch('google.auth.default', return_value=(None, None))
-def test_init_with_cloud_run(mock_auth) -> None:
+@patch("google.auth.default", return_value=(None, None))
+def test_init_with_cloud_run(mock_auth: MagicMock) -> None:
     os.environ["DAPLA_REGION"] = "cloud-run"
     client = GCSFileSystem(project="test-project")
     assert client is not None
 
 
-@patch('google.auth.default', return_value=(None, None))
-def test_init_with_custom_region(mock_auth) -> None:
+@patch("google.auth.default", return_value=(None, None))
+def test_init_with_custom_region(mock_auth: MagicMock) -> None:
     os.environ["DAPLA_REGION"] = "custom-region"
     client = GCSFileSystem(project="test-project")
     assert client is not None
 
 
-@patch('google.auth.default', return_value=(None, None))
-def test_init_with_additional_kwargs(mock_auth) -> None:
+@patch("google.auth.default", return_value=(None, None))
+def test_init_with_additional_kwargs(mock_auth: MagicMock) -> None:
     client = GCSFileSystem(project="test-project", timeout=100)
     assert client is not None