Fix smtp connection test for noop tuple response

providers/smtp/src/airflow/providers/smtp/hooks/smtp.py

@@ -299,9 +299,10 @@ def test_connection(self) -> tuple[bool, str]:
         """Test SMTP connectivity from UI."""
         try:
             smtp_client = self.get_conn()._smtp_client
-            if smtp_client:
+            if smtp_client is not None:
+                smtp_client = cast("smtplib.SMTP_SSL | smtplib.SMTP", smtp_client)
                 status = smtp_client.noop()
-                if status == 250:
+                if status[0] == 250:
                     return True, "Connection successfully tested"
         except Exception as e:
             return False, str(e)

providers/smtp/tests/unit/smtp/hooks/test_smtp.py

@@ -546,6 +546,29 @@ def test_ehlo_called_after_starttls(self, mock_smtplib):
         assert ehlo_call == call.ehlo()
         assert login_call == call.login(SMTP_LOGIN, SMTP_PASSWORD)
 
+    @pytest.mark.parametrize(
+        ("noop_response", "expected_result"),
+        [
+            pytest.param(
+                (250, b"2.0.0 Ok"),
+                (True, "Connection successfully tested"),
+                id="success",
+            ),
+            pytest.param(
+                (421, b"4.3.0 Service not available"),
+                (False, "Failed to establish connection"),
+                id="failure",
+            ),
+        ],
+    )
+    @patch(smtplib_string)
+    def test_test_connection_handles_noop_responses(self, mock_smtplib, noop_response, expected_result):
+        mock_conn = _create_fake_smtp(mock_smtplib)
+        mock_conn.noop.return_value = noop_response
+
+        assert SmtpHook().test_connection() == expected_result
+        mock_conn.noop.assert_called_once_with()
+
 
 @pytest.mark.asyncio
 @pytest.mark.skipif(not AIRFLOW_V_3_1_PLUS, reason="Async support was added to BaseNotifier in 3.1.0")