topology_custom: add deprecated features test

Adds a test which simulates marking a cluster feature as deprecated.

test/topology_custom/test_deprecating_cluster_features.py

@@ -0,0 +1,37 @@
+#
+# Copyright (C) 2023-present ScyllaDB
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+#
+import asyncio
+import time
+
+from test.pylib.manager_client import ManagerClient
+import pytest
+
+
+TEST_FEATURE_ENABLE_ERROR_INJECTION = "features_enable_test_feature"
+TEST_FEATURE_ENABLE_AS_DEPRECATED_ERROR_INJECTION = "features_enable_test_feature_as_deprecated"
+ERROR_INJECTIONS_AT_STARTUP_CONFIG_KEY = "error_injections_at_startup"
+
+
+@pytest.mark.asyncio
+async def test_feature_deprecation_works(manager: ManagerClient) -> None:
+    """Simulate a very old node which, long ago, has enabled some features,
+       persisted them in system.scylla_local, and now some of them became
+       deprecated.
+    """
+
+    # Start the node, enable the feature
+    srv = await manager.server_add(config={
+        ERROR_INJECTIONS_AT_STARTUP_CONFIG_KEY: [TEST_FEATURE_ENABLE_ERROR_INJECTION]
+    })
+    await manager.server_start(srv.server_id)
+
+    # Restart the node, but this time the feature is deprecated
+    await manager.server_stop_gracefully(srv.server_id)
+    await manager.server_update_config(srv.server_id, ERROR_INJECTIONS_AT_STARTUP_CONFIG_KEY,
+                                       [TEST_FEATURE_ENABLE_AS_DEPRECATED_ERROR_INJECTION])
+    await manager.server_start(srv.server_id)
+
+    # The node should restart successfully