diff --git a/tests/unit/services/test_comms_protocol.py b/tests/unit/services/test_comms_protocol.py
new file mode 100644
index 0000000..904a692
--- /dev/null
+++ b/tests/unit/services/test_comms_protocol.py
@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+from ariadne.services import comms_protocol as protocol
+
+
+def test_canon_user_preserves_and_normalizes_matrix_ids() -> None:
+    assert protocol._canon_user("@alice:matrix.example", "matrix.example") == "@alice:matrix.example"
+    assert protocol._canon_user("alice:matrix.example", "matrix.example") == "@alice:matrix.example"
+    assert protocol._canon_user("alice", "matrix.example") == "@alice:matrix.example"
+
+
+def test_display_rename_required_for_missing_names() -> None:
+    assert protocol._needs_rename_display(None) is True