Add test for nested nodes, add checks for presence of nodes in pre-processed config

tests/integration/test_config_hidden_attributes/configs/config.xml

@@ -1,3 +1,11 @@
 <clickhouse>
     <max_table_size_to_drop hidden="true">60000000000</max_table_size_to_drop>
+    <max_partition_size_to_drop hidden="false">40000000000</max_partition_size_to_drop>
+    <named_collections hidden="true">
+        <name>
+            <key_1>value</key_1>
+            <key_2>value_2</key_2>
+            <url>https://connection.url/</url>
+        </name>
+    </named_collections>
 </clickhouse>

tests/integration/test_config_hidden_attributes/configs/users.xml

@@ -0,0 +1,7 @@
+<clickhouse>
+    <users>
+        <default>
+            <named_collection_control>1</named_collection_control>
+        </default>
+    </users>
+</clickhouse>

tests/integration/test_config_hidden_attributes/test.py

@@ -2,8 +2,11 @@ import pytest
 import os
 from helpers.cluster import ClickHouseCluster
 
+
 cluster = ClickHouseCluster(__file__)
-node = cluster.add_instance("node", main_configs=["configs/config.xml"])
+node = cluster.add_instance(
+    "node", main_configs=["configs/config.xml"], user_configs=["configs/users.xml"]
+)
 
 
 @pytest.fixture(scope="module")
@@ -23,3 +26,16 @@ def test_hidden(started_cluster):
         )
         == "60000000000\n"
     )
+    assert (
+        node.query(
+            "select value from system.server_settings where name ='max_partition_size_to_drop'"
+        )
+        == "40000000000\n"
+    )
+    assert "key_1" in node.query("select collection from system.named_collections")
+    out = node.exec_in_container(
+        ["cat", "/var/lib/clickhouse/preprocessed_configs/config.xml"]
+    )
+    assert "max_table_size_to_drop" not in out
+    assert "max_partition_size_to_drop" in out
+    assert "named_collections" not in out