test: finalize CI test coverage and fix dependency import path

requirements.txt

@@ -1,2 +1,2 @@
-aiosmtpd>=1.6.3
+aiosmtpd>=1.4.6,<1.5
 pytest>=8.0.0

tests/conftest.py

@@ -0,0 +1,7 @@
+import os
+import sys
+
+# Ensure the project root is on sys.path when running tests.
+ROOT = os.path.dirname(os.path.dirname(__file__))
+if ROOT not in sys.path:
+    sys.path.insert(0, ROOT)

tests/test_proxy_server.py

@@ -114,7 +114,7 @@ def test_smtp_proxy_handler_forwards_message_over_ssl(monkeypatch):
     assert captured["instance"].logged_in is True
     assert captured["instance"].sent[0] == "from@example.com"
     assert captured["instance"].sent[1] == ["to@example.com"]
-    assert b"Subject: Test" in captured["instance"].sent[2]
+    assert "Subject: Test" in captured["instance"].sent[2]
 
     Settings.BACKEND_SMTP_USE_SSL = previous_ssl
     Settings.BACKEND_SMTP_USER = previous_user