test: Test password-only AUTH for Redis versions below 6.0.0 without HELLO command

Author: zeze1004

tests/test_connection.py

@@ -264,6 +264,58 @@ def test_on_connect_fail_auth(self, mock_read_response, mock_send_command):
         mock_send_command.assert_called()
         mock_read_response.assert_called()
 
+    @patch.object(Connection, 'send_command')
+    @patch.object(Connection, 'read_response')
+    def test_on_connect_auth_with_password_only(
+            self, mock_read_response, mock_send_command):
+        """Test on_connect handling of password-only AUTH for Redis versions below 6.0.0 without HELLO command"""
+        conn = Connection()
+
+        conn._parser = MagicMock()
+        conn._parser.on_connect.return_value = None
+        conn.credential_provider = None
+        conn.username = None
+        conn.password = "password"
+        conn.protocol = 1
+        conn.client_name = "test-client"
+        conn.lib_name = "test"
+        conn.lib_version = "1234"
+        conn.db = 1
+        conn.client_cache = True
+
+        # command response to simulate Redis < 6.0.0 behavior
+        mock_read_response.side_effect = itertools.cycle([
+            Exception("ERR HELLO"),  # HELLO (fails)
+            b'QUEUED',  # MULTI
+            b'QUEUED',  # AUTH
+            b'QUEUED',  # CLIENT SETNAME
+            b'QUEUED',  # CLIENT SETINFO LIB-NAME
+            b'QUEUED',  # CLIENT SETINFO LIB-VER
+            b'QUEUED',  # SELECT
+            b'QUEUED',  # CLIENT TRACKING ON
+            [
+                b'OK',                           # AUTH response
+                b'OK',                           # CLIENT SETNAME response
+                b'OK',                           # CLIENT SETINFO LIB-NAME response
+                b'OK',                           # CLIENT SETINFO LIB-VER response
+                b'OK',                           # SELECT response
+                b'OK'                            # CLIENT TRACKING ON response
+            ]
+        ])
+
+        conn.on_connect()
+
+        mock_send_command.assert_any_call('HELLO', 1, 'AUTH', 'default', 'password'),
+        mock_send_command.assert_any_call('MULTI'),
+        mock_send_command.assert_any_call(
+            'AUTH', 'default', 'password', check_health=False)
+        mock_send_command.assert_any_call('CLIENT', 'SETNAME', 'test-client')
+        mock_send_command.assert_any_call('CLIENT', 'SETINFO', 'LIB-NAME', 'test')
+        mock_send_command.assert_any_call('CLIENT', 'SETINFO', 'LIB-VER', '1234')
+        mock_send_command.assert_any_call('SELECT', 1)
+        mock_send_command.assert_any_call('CLIENT', 'TRACKING', 'ON')
+        mock_send_command.assert_any_call('EXEC')
+        mock_read_response.assert_called()
 
 
 @pytest.mark.onlynoncluster