Added test case to verify TLS 1.3 auto-negotiation support

vertica_python/tests/integration_tests/test_tls.py

@@ -298,6 +298,57 @@ def test_sslcontext_verify_full(self):
             res = self._query_and_fetchone(self.SSL_STATE_SQL)
             self.assertEqual(res[0], 'Server')
 
+    def test_tls13_support_auto_negotiation(self):
+        """
+        Verify that the client supports TLS 1.3 negotiation.
+        If the server supports TLS 1.3, the connection should establish using it.
+        If the server supports only TLS 1.2, the connection should still succeed.
+        """
+
+        # Set up server certificates and enable TLS
+        CA_cert = self._generate_and_set_certificates()
+
+        # Create SSL context allowing both TLS 1.2 and 1.3
+        ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        ssl_context.verify_mode = ssl.CERT_REQUIRED
+        ssl_context.check_hostname = True
+        ssl_context.load_verify_locations(cadata=CA_cert)
+
+        # Assign SSL context to connection info
+        self._conn_info['ssl'] = ssl_context
+
+        with self._connect() as conn:
+            cur = conn.cursor()
+            res = self._query_and_fetchone(self.SSL_STATE_SQL)
+            self.assertEqual(res[0], 'Server')
+
+            # Try to get the negotiated TLS version from the socket
+            tls_version = None
+            try:
+                if hasattr(conn._socket, "_sslobj"):
+                    tls_version = conn._socket._sslobj.version()
+                elif hasattr(conn._socket, "version"):
+                    tls_version = conn._socket.version()
+            except Exception:
+                pass
+
+            # Log version for debug (optional)
+            print(f"Negotiated TLS version: {tls_version}")
+
+            # Ensure TLS negotiation was successful
+            self.assertIsNotNone(tls_version, "Could not determine negotiated TLS version")
+
+            # Accept both 1.2 and 1.3, but prefer 1.3 if available
+            self.assertIn(
+                tls_version, ("TLSv1.2", "TLSv1.3"),
+                msg=f"Unexpected TLS version negotiated: {tls_version}"
+            )
+
+            if tls_version == "TLSv1.3":
+                print("TLS 1.3 is successfully negotiated and supported.")
+            else:
+                print("Fell back to TLS 1.2 (TLS 1.3 not supported by server).")
+
     def test_sslcontext_mutual_TLS(self):
         # Setting certificates with TLS configuration
         CA_cert = self._generate_and_set_certificates(mutual_mode=True)