Added test case to verify TLS 1.3 auto-negotiation support (#575)

Co-authored-by: root <[email protected]>

Author: sharmagot

vertica_python/tests/integration_tests/test_tls.py

@@ -298,6 +298,59 @@ def test_sslcontext_verify_full(self):
             res = self._query_and_fetchone(self.SSL_STATE_SQL)
             self.assertEqual(res[0], 'Server')
 
+    def _get_tls_version(self, conn):
+        sock = getattr(conn, '_socket', None)
+        if not sock:
+            return None
+
+        if hasattr(sock, 'version') and callable(sock.version):
+            return sock.version()
+
+        ssl_obj = getattr(sock, '_sslobj', None)
+        if ssl_obj and hasattr(ssl_obj, 'version'):
+            return ssl_obj.version()
+
+        return None
+
+    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
+        try:
+            CA_cert = self._generate_and_set_certificates()
+        except Exception:
+            self.skipTest("Failed to generate CA certificates; skipping TLS test")
+
+        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)
+
+        self._conn_info['ssl'] = ssl_context
+        self._conn_info['tlsmode'] = 'require'
+
+        with self._connect() as conn:
+            # First ensure TLS really got enabled on server
+            res = self._query_and_fetchone(self.SSL_STATE_SQL)
+            if res[0] != 'Server':
+                self.skipTest("TLS is not configured on server")
+
+            # Prefer public API, fall back only if needed
+            tls_version = self._get_tls_version(conn)
+
+            if tls_version is None:
+                self.skipTest("Could not determine negotiated TLS version.")
+
+            self.assertIn(
+                tls_version,
+                ("TLSv1.2", "TLSv1.3"),
+                msg=f"Unexpected TLS version negotiated: {tls_version}"
+            )
+
     def test_sslcontext_mutual_TLS(self):
         # Setting certificates with TLS configuration
         CA_cert = self._generate_and_set_certificates(mutual_mode=True)