diff --git a/tests/unit/test_compose_run_log_format.py b/tests/unit/test_compose_run_log_format.py
index 878ead6..e63f5be 100644
--- a/tests/unit/test_compose_run_log_format.py
+++ b/tests/unit/test_compose_run_log_format.py
@@ -8,10 +8,10 @@ from podman_compose import Podman
 
 
 class DummyReader:
-    def __init__(self, data=[]):
-        self.data = data
+    def __init__(self, data=None):
+        self.data = data or []
 
-    async def readuntil(self, x):
+    async def readuntil(self, _):
         return self.data.pop(0)
 
     def at_eof(self):