diff --git a/src/grafana_agent.py b/src/grafana_agent.py
index 92338e8..95aa11c 100644
--- a/src/grafana_agent.py
+++ b/src/grafana_agent.py
@@ -126,6 +126,7 @@ def __new__(cls, *args: Any, **kwargs: Dict[Any, Any]):
 
     def __init__(self, *args):
         super().__init__(*args)
+        os.umask(0o077)
 
         # Property to facilitate centralized status update
         self.status = CompoundStatus()
@@ -133,13 +134,13 @@ def __init__(self, *args):
         charm_root = self.charm_dir.absolute()
         self.loki_rules_paths = RulesMapping(
             # TODO how to inject topology only for this charm's own rules?
-            # FIXED: this is already handled by re-using the *Rules classes
+            # FIXED: this is already handled by reusing the *Rules classes
             src=charm_root.joinpath(*LOKI_RULES_SRC_PATH.split("/")),
             dest=charm_root.joinpath(*LOKI_RULES_DEST_PATH.split("/")),
         )
         self.metrics_rules_paths = RulesMapping(
             # TODO how to inject topology only for this charm's own rules?
-            # FIXED: this is already handled by re-using the *Rules classes
+            # FIXED: this is already handled by reusing the *Rules classes
             src=charm_root.joinpath(*METRICS_RULES_SRC_PATH.split("/")),
             dest=charm_root.joinpath(*METRICS_RULES_DEST_PATH.split("/")),
         )
diff --git a/tests/unit/conftest.py b/tests/unit/conftest.py
new file mode 100644
index 0000000..6cf36bc
--- /dev/null
+++ b/tests/unit/conftest.py
@@ -0,0 +1,12 @@
+from unittest.mock import patch
+
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def patch_buffer_file_for_charm_tracing(tmp_path):
+    with patch(
+        "charms.tempo_coordinator_k8s.v0.charm_tracing.BUFFER_DEFAULT_CACHE_FILE_NAME",
+        str(tmp_path / "foo.json"),
+    ):
+        yield