/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *     https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.configuration2.tree;
  
  import static org.apache.commons.configuration2.tree.NodeStructureHelper.ROOT_AUTHORS_TREE;
  import static org.apache.commons.configuration2.tree.NodeStructureHelper.ROOT_PERSONAE_TREE;
  import static org.apache.commons.configuration2.tree.NodeStructureHelper.nodeForKey;
  import static org.apache.commons.configuration2.tree.NodeStructureHelper.nodePathWithEndNode;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNotEquals;
  import static org.junit.jupiter.api.Assertions.assertNotNull;
  import static org.junit.jupiter.api.Assertions.assertNull;
  import static org.junit.jupiter.api.Assertions.assertSame;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  import static org.mockito.ArgumentMatchers.any;
  import static org.mockito.ArgumentMatchers.eq;
  import static org.mockito.Mockito.mock;
  import static org.mockito.Mockito.when;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Set;
  import java.util.concurrent.CountDownLatch;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import org.junit.jupiter.api.Test;
  
  /**
   * Test class for {@code InMemoryNodeModel}.
   */
  public class TestInMemoryNodeModel {
  
      /** Constant for a test key. */
      private static final String KEY = "aTestKey";
  
      /**
       * Helper method for checking whether the expected nodes are encountered on a path from a start node to the root node.
       *
       * @param model the node model
       * @param node the start node in the path
       * @param path an array with the expected node names on the path
       */
      private static void checkPathToRoot(final InMemoryNodeModel model, ImmutableNode node, final String... path) {
          final NodeHandler<ImmutableNode> handler = model.getNodeHandler();
          for (int i = path.length - 1; i >= 0; i--) {
              node = handler.getParent(node);
              assertEquals(path[i], node.getNodeName());
          }
          assertSame(model.getRootNode(), handler.getParent(node));
      }
  
      /**
       * Creates a mock for a {@code NodeKeyResolver}.
       *
       * @return the mock for the resolver
       */
      @SuppressWarnings("unchecked")
      private static NodeKeyResolver<ImmutableNode> createResolver() {
          return mock(NodeKeyResolver.class);
      }
  
      /**
       * Helper method for testing the behavior of addNodes() if no nodes to be added are provided.
       *
       * @param newNodes the collection with new nodes
       */
      private void checkAddNodesNoNodes(final Collection<ImmutableNode> newNodes) {
          final NodeKeyResolver<ImmutableNode> resolver = createResolver();
          final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_AUTHORS_TREE);
  
          model.addNodes(KEY, newNodes, resolver);
          assertSame(NodeStructureHelper.ROOT_AUTHORS_TREE, model.getRootNode());
      }
  
      /**
      * Helper method for testing whether nodes removed from the model can no longer be looked up in the parent mapping.
      *
      * @param pathToRemove the path to the node to be removed
      * @param nodeToCheck the node to check in the parent mapping
      */
     private void checkClearTreeUpdatedParentMapping(final String pathToRemove, final ImmutableNode nodeToCheck) {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         final QueryResult<ImmutableNode> result = QueryResult.createNodeResult(nodeForKey(model, pathToRemove));
 
         when(resolver.resolveKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(Collections.singletonList(result));
 
         model.clearTree(KEY, resolver);
         final NodeHandler<ImmutableNode> nodeHandler = model.getNodeHandler();
         assertThrows(IllegalArgumentException.class, () -> nodeHandler.getParent(nodeToCheck));
     }
 
     /**
      * Tests an add nodes operation if an empty collection is passed in.
      */
     @Test
     void testAddNodesEmptyCollection() {
         checkAddNodesNoNodes(Collections.<ImmutableNode>emptySet());
     }
 
     /**
      * Tests an add nodes operation if a null collection is passed in.
      */
     @Test
     void testAddNodesNullCollection() {
         checkAddNodesNoNodes(null);
     }
 
     /**
      * Tries to add new nodes if the key references an attribute.
      */
     @Test
     void testAddNodesToAttribute() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_AUTHORS_TREE);
         when(resolver.resolveKey(NodeStructureHelper.ROOT_AUTHORS_TREE, KEY, model.getNodeHandler()))
                 .thenReturn(Collections.singletonList(QueryResult.createAttributeResult(nodeForKey(model, NodeStructureHelper.author(1)), "test")));
 
         final ImmutableNode newNode = new ImmutableNode.Builder().name("newNode").create();
         final Set<ImmutableNode> nodes = Collections.singleton(newNode);
         assertThrows(IllegalArgumentException.class, () -> model.addNodes(KEY, nodes, resolver));
     }
 
     /**
      * Tests whether new nodes can be added to an existing node in the model.
      */
     @Test
     void testAddNodesToExistingNode() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_AUTHORS_TREE);
         final String key = NodeStructureHelper.author(0);
         final ImmutableNode newWork1 = new ImmutableNode.Builder().name("King Lear").create();
         final ImmutableNode newWork2 = new ImmutableNode.Builder().name("The Taming of the Shrew").create();
         when(resolver.resolveKey(NodeStructureHelper.ROOT_AUTHORS_TREE, KEY, model.getNodeHandler()))
                 .thenReturn(Collections.singletonList(QueryResult.createNodeResult(nodeForKey(model, key))));
 
         model.addNodes(KEY, Arrays.asList(newWork1, newWork2), resolver);
         final ImmutableNode node = nodeForKey(model, key);
         final int size = node.getChildren().size();
         assertSame(newWork1, node.getChildren().get(size - 2));
         assertSame(newWork2, node.getChildren().get(size - 1));
     }
 
     /**
      * Tries to add new nodes to an non-existing key pointing to an attribute.
      */
     @Test
     void testAddNodesToNewAttributeKey() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_AUTHORS_TREE);
         when(resolver.resolveKey(NodeStructureHelper.ROOT_AUTHORS_TREE, KEY, model.getNodeHandler()))
                 .thenReturn(Collections.<QueryResult<ImmutableNode>>emptyList());
         when(resolver.resolveAddKey(NodeStructureHelper.ROOT_AUTHORS_TREE, KEY, model.getNodeHandler()))
                 .thenReturn(new NodeAddData<>(NodeStructureHelper.ROOT_AUTHORS_TREE, "test", true, null));
 
         final ImmutableNode newNode = new ImmutableNode.Builder().name("newNode").create();
         final Set<ImmutableNode> nodes = Collections.singleton(newNode);
         assertThrows(IllegalArgumentException.class, () -> model.addNodes(KEY, nodes, resolver));
     }
 
     /**
      * Tests whether nodes can be added to a node which has to be created.
      */
     @Test
     void testAddNodesToNewNode() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_AUTHORS_TREE);
         final String newAuthor = "Goethe";
         final String newWork = "Faust";
         final String newPersona = "Mephisto";
 
         when(resolver.resolveKey(NodeStructureHelper.ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(new ArrayList<>(0));
         when(resolver.resolveAddKey(NodeStructureHelper.ROOT_AUTHORS_TREE, KEY, model.getNodeHandler()))
                 .thenReturn(new NodeAddData<>(NodeStructureHelper.ROOT_AUTHORS_TREE, newWork, false, Arrays.asList(newAuthor)));
 
         final ImmutableNode personaNode = new ImmutableNode.Builder().name(newPersona).create();
         model.addNodes(KEY, Collections.singleton(personaNode), resolver);
         assertSame(personaNode, nodeForKey(model, newAuthor + "/" + newWork + "/" + newPersona));
     }
 
     /**
      * Tests whether an attribute property can be added if there are no path nodes.
      */
     @Test
     void testAddPropertyAttributeNoPathNodes() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final NodeAddData<ImmutableNode> addData = new NodeAddData<>(nodeForKey(ROOT_AUTHORS_TREE, "Shakespeare/The Tempest"), "year", true, null);
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         when(resolver.resolveAddKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(addData);
 
         model.addProperty(KEY, Collections.singleton(1611), resolver);
         final ImmutableNode node = nodeForKey(model, "Shakespeare/The Tempest");
         assertEquals(1611, node.getAttributes().get("year"));
     }
 
     /**
      * Tests whether an attribute can be added if there are some path nodes.
      */
     @Test
     void testAddPropertyAttributeWithPathNodes() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final NodeAddData<ImmutableNode> addData = new NodeAddData<>(nodeForKey(ROOT_AUTHORS_TREE, "Homer/Ilias"), "number", true,
             Arrays.asList("scenes", "scene"));
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         when(resolver.resolveAddKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(addData);
 
         model.addProperty(KEY, Collections.singleton(1), resolver);
         final ImmutableNode node = nodeForKey(model, "Homer/Ilias/scenes/scene");
         assertEquals(1, node.getAttributes().get("number"));
     }
 
     /**
      * Tests the special case that an attribute is added with a single path node.
      */
     @Test
     void testAddPropertyAttributeWithSinglePathNode() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final NodeAddData<ImmutableNode> addData = new NodeAddData<>(nodeForKey(ROOT_AUTHORS_TREE, NodeStructureHelper.author(0)), "year", true,
             Arrays.asList("dateOfBirth"));
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         when(resolver.resolveAddKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(addData);
 
         final Integer year = 1564;
         model.addProperty(KEY, Collections.singleton(year), resolver);
         final ImmutableNode node = nodeForKey(model, "Shakespeare/dateOfBirth");
         assertEquals(year, node.getAttributes().get("year"));
     }
 
     /**
      * Tests whether a property can be added if there are no intermediate path nodes.
      */
     @Test
     void testAddPropertyNoPathNodes() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final NodeAddData<ImmutableNode> addData = new NodeAddData<>(nodeForKey(ROOT_AUTHORS_TREE, "Homer"), "work", false, null);
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         when(resolver.resolveAddKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(addData);
 
         model.addProperty(KEY, Collections.singleton("Odyssee"), resolver);
         final ImmutableNode node = nodeForKey(model, "Homer/work");
         assertEquals("Odyssee", node.getValue());
         assertNotNull(nodeForKey(model, "Homer/Ilias/Hektor"));
     }
 
     /**
      * Tests an addProperty() operation if no values are provided.
      */
     @Test
     void testAddPropertyNoValues() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         model.addProperty(KEY, Collections.emptySet(), resolver);
         assertSame(ROOT_AUTHORS_TREE, model.getRootNode());
     }
 
     /**
      * Tests whether the parent node references are updated when nodes are added.
      */
     @Test
     void testAddPropertyUpdateParentReferences() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final NodeAddData<ImmutableNode> addData = new NodeAddData<>(nodeForKey(ROOT_AUTHORS_TREE, "Homer/Ilias"), "location", false,
             Collections.singleton("locations"));
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         when(resolver.resolveAddKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(addData);
 
         final String[] locations = {"Troja", "Beach", "Olympos"};
 
         model.addProperty(KEY, Arrays.asList(locations), resolver);
         final String[] path = {"Homer", "Ilias", "locations"};
         final ImmutableNode node = nodeForKey(model, nodePathWithEndNode("location(1)", path));
         checkPathToRoot(model, node, path);
     }
 
     /**
      * Tests whether a property can be added to the node model if there are some additional path nodes to be created.
      */
     @Test
     void testAddPropertyWithPathNodes() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final NodeAddData<ImmutableNode> addData = new NodeAddData<>(nodeForKey(ROOT_AUTHORS_TREE, "Homer/Ilias"), "location", false,
             Collections.singleton("locations"));
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         when(resolver.resolveAddKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(addData);
 
         final String[] locations = {"Troja", "Beach", "Olympos"};
 
         model.addProperty(KEY, Arrays.asList(locations), resolver);
         final ImmutableNode nodeLocs = nodeForKey(model, "Homer/Ilias/locations");
         assertEquals(locations.length, nodeLocs.getChildren().size());
         int idx = 0;
         for (final ImmutableNode c : nodeLocs) {
             assertEquals("location", c.getNodeName());
             assertEquals(locations[idx], c.getValue());
             assertTrue(c.getChildren().isEmpty());
             assertTrue(c.getAttributes().isEmpty());
             idx++;
         }
         assertNotNull(nodeForKey(model, "Homer/Ilias/Hektor"));
     }
 
     /**
      * Tests whether the whole node structure can be cleared.
      */
     @Test
     void testClear() {
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         model.clear(createResolver());
         assertFalse(model.getNodeHandler().isDefined(model.getRootNode()));
         assertEquals(ROOT_AUTHORS_TREE.getNodeName(), model.getRootNode().getNodeName());
     }
 
     /**
      * Tests whether a property value stored as an attribute can be cleared.
      */
     @Test
     void testClearPropertyAttribute() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
         final String nodeKey = "Prospero/The Tempest/" + NodeStructureHelper.ELEM_ORG_VALUE;
 
         when(resolver.resolveKey(model.getRootNode(), KEY, model.getNodeHandler()))
                 .thenReturn(Collections.singletonList(QueryResult.createAttributeResult(nodeForKey(model, nodeKey), NodeStructureHelper.ATTR_TESTED)));
 
         model.clearProperty(KEY, resolver);
         final ImmutableNode node = nodeForKey(model, nodeKey);
         assertTrue(node.getAttributes().isEmpty());
     }
 
     /**
      * Tests whether a property value can be cleared on a node.
      */
     @Test
     void testClearPropertyNode() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
         final String nodeKey = "Ariel/The Tempest/" + NodeStructureHelper.ELEM_ORG_VALUE;
         when(resolver.resolveKey(model.getRootNode(), KEY, model.getNodeHandler()))
                 .thenReturn(Collections.singletonList(QueryResult.createNodeResult(nodeForKey(model, nodeKey))));
 
         model.clearProperty(KEY, resolver);
         final ImmutableNode node = nodeForKey(model, nodeKey);
         assertNull(node.getValue());
     }
 
     /**
      * Tests clearProperty() for a non existing property.
      */
     @Test
     void testClearPropertyNonExisting() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
 
         when(resolver.resolveKey(model.getRootNode(), KEY, model.getNodeHandler())).thenReturn(Collections.<QueryResult<ImmutableNode>>emptyList());
 
         final TreeData treeDataOld = model.getTreeData();
         model.clearProperty(KEY, resolver);
         assertNotNull(model.getNodeHandler().getRootNode());
         assertSame(treeDataOld, model.getTreeData());
     }
 
     /**
      * Tests whether attributes can be cleared with clearTree().
      */
     @Test
     void testClearTreeAttribute() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_PERSONAE_TREE);
         final String nodeName = "Puck";
         final QueryResult<ImmutableNode> result = QueryResult.createAttributeResult(nodeForKey(model, nodeName), NodeStructureHelper.ATTR_AUTHOR);
 
         when(resolver.resolveKey(ROOT_PERSONAE_TREE, KEY, model.getNodeHandler())).thenReturn(Collections.singletonList(result));
 
         final List<QueryResult<ImmutableNode>> removed = model.clearTree(KEY, resolver);
         final ImmutableNode node = nodeForKey(model, nodeName);
         assertTrue(node.getAttributes().isEmpty());
         assertEquals(1, removed.size());
         assertTrue(removed.contains(result));
     }
 
     /**
      * Tests whether the children of removed nodes are also removed from the parent mapping.
      */
     @Test
     void testClearTreeChildrenRemovedFromParentMapping() {
         final String path = "Homer/Ilias";
         checkClearTreeUpdatedParentMapping(path, nodeForKey(ROOT_AUTHORS_TREE, path + "/Achilles"));
     }
 
     /**
      * Tests whether a removed node can no longer be passed to getParent().
      */
     @Test
     void testClearTreeNodeRemovedFromParentMapping() {
         final String path = "Homer/Ilias/Achilles";
         checkClearTreeUpdatedParentMapping(path, nodeForKey(ROOT_AUTHORS_TREE, path));
     }
 
     /**
      * Tests whether a clearTree() operation can be performed if only nodes are involved.
      */
     @Test
     void testClearTreeNodes() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         final QueryResult<ImmutableNode> result = QueryResult.createNodeResult(nodeForKey(model, "Homer/Ilias/Achilles"));
 
         when(resolver.resolveKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(Collections.singletonList(result));
 
         final List<QueryResult<ImmutableNode>> removed = model.clearTree(KEY, resolver);
         final ImmutableNode node = nodeForKey(model, "Homer/Ilias");
         assertEquals(2, node.getChildren().size());
         for (final ImmutableNode c : node) {
             assertNotEquals(result.getNode().getNodeName(), c.getNodeName());
         }
         assertEquals(1, removed.size());
         assertTrue(removed.contains(result));
     }
 
     /**
      * Tests whether both nodes and attributes can be removed by a clearTree() operation. We remove all attributes and
      * children from a node. The node becomes undefined and should be removed.
      */
     @Test
     void testClearTreeNodesAndAttributes() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_PERSONAE_TREE);
         final String nodeName = "Puck";
         final ImmutableNode orgNode = nodeForKey(model, nodeName);
         final List<QueryResult<ImmutableNode>> results = new ArrayList<>(2);
         results.add(QueryResult.createAttributeResult(orgNode, NodeStructureHelper.ATTR_AUTHOR));
         results.add(QueryResult.createNodeResult(orgNode.getChildren().get(0)));
 
         when(resolver.resolveKey(ROOT_PERSONAE_TREE, KEY, model.getNodeHandler())).thenReturn(results);
 
         model.clearTree(KEY, resolver);
         assertThrows(NoSuchElementException.class, () -> nodeForKey(model, nodeName));
     }
 
     /**
      * Tests clearTree() if the passed in key does not exist.
      */
     @Test
     void testClearTreeNonExistingKey() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_PERSONAE_TREE);
 
         when(resolver.resolveKey(ROOT_PERSONAE_TREE, KEY, model.getNodeHandler())).thenReturn(Collections.<QueryResult<ImmutableNode>>emptyList());
 
         final TreeData treeDataOld = model.getTreeData();
         assertTrue(model.clearTree(KEY, resolver).isEmpty());
         assertNotNull(model.getNodeHandler().getRootNode());
         assertSame(treeDataOld, model.getTreeData());
     }
 
     /**
      * Tests whether undefined nodes are removed from the hierarchy when clearing properties.
      */
     @Test
     void testClearTreeRemoveUndefinedNodes() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         final ImmutableNode node = nodeForKey(model, "Homer/Ilias");
         final List<QueryResult<ImmutableNode>> results = new ArrayList<>(node.getChildren().size());
         for (final ImmutableNode child : node) {
             results.add(QueryResult.createNodeResult(child));
         }
 
         when(resolver.resolveKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(results);
 
         model.clearTree(KEY, resolver);
         assertEquals(NodeStructureHelper.authorsLength() - 1, model.getRootNode().getChildren().size());
         for (final ImmutableNode child : model.getRootNode()) {
             assertNotEquals("Homer", child.getNodeName());
         }
     }
 
     /**
      * Tests a clearTree() operation which should yield an empty tree structure.
      */
     @Test
     void testClearTreeResultIsEmpty() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final ImmutableNode child = new ImmutableNode.Builder().name("child").value("test").create();
         final ImmutableNode root = new ImmutableNode.Builder(1).addChild(child).create();
         final InMemoryNodeModel model = new InMemoryNodeModel(root);
 
         when(resolver.resolveKey(root, KEY, model.getNodeHandler())).thenReturn(Collections.singletonList(QueryResult.createNodeResult(child)));
 
         model.clearTree(KEY, resolver);
         assertFalse(model.getNodeHandler().isDefined(model.getRootNode()));
     }
 
     /**
      * Tests whether clearTree() handles the root node in a special way.
      */
     @Test
     void testClearTreeRootNode() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         final List<QueryResult<ImmutableNode>> results = new ArrayList<>(2);
         results.add(QueryResult.createNodeResult(nodeForKey(model, NodeStructureHelper.author(0))));
         results.add(QueryResult.createNodeResult(ROOT_AUTHORS_TREE));
 
         when(resolver.resolveKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(results);
 
         model.clearTree(KEY, resolver);
         assertFalse(model.getNodeHandler().isDefined(model.getRootNode()));
     }
 
     /**
      * Tests whether references to parent nodes are updated correctly when clearing properties.
      */
     @Test
     void testClearTreeUpdateParentReferences() {
         final String[] path = {"Homer", "Ilias"};
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         final QueryResult<ImmutableNode> result = QueryResult.createNodeResult(nodeForKey(model, nodePathWithEndNode("Achilles", path)));
 
         when(resolver.resolveKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(Collections.singletonList(result));
 
         model.clearTree(KEY, resolver);
         checkPathToRoot(model, nodeForKey(model, nodePathWithEndNode("Hektor", path)), path);
     }
 
     /**
      * Tests whether the replacement mapping is automatically compacted if it gets too large.
      */
     @Test
     void testCompactReplacementMapping() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         final int numberOfOperations = 200;
         final String key = "Homer/Ilias";
         for (int i = 0; i < numberOfOperations; i++) {
             final int index = i;
             when(resolver.resolveAddKey(any(), eq(KEY), any())).thenAnswer(invocation -> {
                 assertSame(model.getRootNode(), invocation.getArgument(0));
                 final ImmutableNode addParent = nodeForKey(model, key);
                 return new NodeAddData<>(addParent, "Warrior" + index, false, null);
             });
         }
 
         for (int i = 0; i < numberOfOperations; i++) {
             model.addProperty(KEY, Collections.singleton(i), resolver);
         }
         final ImmutableNode orgNode = nodeForKey(ROOT_AUTHORS_TREE, key);
         final ImmutableNode changedNode = nodeForKey(model, key);
         assertEquals(orgNode.getChildren().size() + numberOfOperations, changedNode.getChildren().size());
         final Map<ImmutableNode, ImmutableNode> replacementMapping = model.getTreeData().copyReplacementMapping();
         assertTrue(replacementMapping.size() < numberOfOperations);
     }
 
     /**
      * Tests whether concurrent updates of the model are handled correctly. This test adds a number of authors in parallel.
      * Then it is checked whether all authors have been added correctly.
      */
     @Test
     void testConcurrentUpdate() throws InterruptedException {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_AUTHORS_TREE);
 
         when(resolver.resolveAddKey(any(), eq(KEY), any())).thenAnswer(invocation -> {
             final ImmutableNode addParent = invocation.getArgument(0, ImmutableNode.class);
             return new NodeAddData<>(addParent, "name", false, Collections.singleton("author"));
         });
 
         final CountDownLatch latch = new CountDownLatch(1);
         final String authorPrefix = "newAuthor";
         final int threadCount = 32;
         final Thread[] threads = new Thread[threadCount];
         for (int i = 0; i < threadCount; i++) {
             final String authorName = authorPrefix + i;
             threads[i] = new Thread(() -> {
                 try {
                     latch.await();
                     model.addProperty(KEY, Collections.singleton(authorName), resolver);
                 } catch (final InterruptedException iex) {
                     // ignore
                 }
             });
             threads[i].start();
         }
         latch.countDown();
         for (final Thread t : threads) {
             t.join();
         }
 
         final Pattern patternAuthorName = Pattern.compile(Pattern.quote(authorPrefix) + "(\\d+)");
         final Set<Integer> indices = new HashSet<>();
         for (int i = 0; i < threadCount; i++) {
             final ImmutableNode node = nodeForKey(model, "author(" + i + ")/name");
             final Matcher m = patternAuthorName.matcher(String.valueOf(node.getValue()));
             assertTrue(m.matches(), "Wrong value: " + node.getValue());
             final int idx = Integer.parseInt(m.group(1));
             assertTrue(idx >= 0 && idx < threadCount, "Invalid index: " + idx);
             indices.add(idx);
         }
         assertEquals(threadCount, indices.size());
     }
 
     /**
      * Tests whether the model's data can be represented as immutable node objects (which is trivial in this case).
      */
     @Test
     void testGetInMemoryRepresentation() {
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_AUTHORS_TREE);
         assertSame(NodeStructureHelper.ROOT_AUTHORS_TREE, model.getInMemoryRepresentation());
     }
 
     /**
      * Tests whether the correct node handler is returned.
      */
     @Test
     void testGetNodeHandler() {
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_PERSONAE_TREE);
         assertSame(model.getTreeData(), model.getNodeHandler());
     }
 
     /**
      * Tests whether the correct root node is returned if a tree was passed at construction time.
      */
     @Test
     void testGetRootNodeFromConstructor() {
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
         assertSame(ROOT_AUTHORS_TREE, model.getRootNode());
     }
 
     /**
      * Tests whether an undefined default root node is created if none is specified.
      */
     @Test
     void testInitDefaultRoot() {
         final InMemoryNodeModel model = new InMemoryNodeModel();
         final ImmutableNode root = model.getRootNode();
         assertNull(root.getNodeName());
         assertNull(root.getValue());
         assertTrue(root.getChildren().isEmpty());
         assertTrue(root.getAttributes().isEmpty());
     }
 
     /**
      * Tests whether setProperty() can handle changes in node values.
      */
     @Test
     void testSetPropertyChangedValues() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
         final String nodeKey = "Ariel/The Tempest/" + NodeStructureHelper.ELEM_ORG_VALUE;
         final Map<QueryResult<ImmutableNode>, Object> changedValues = new HashMap<>();
         final String newValue = "of course";
         final ImmutableNode changedNode = nodeForKey(model, nodeKey);
         changedValues.put(QueryResult.createAttributeResult(changedNode, NodeStructureHelper.ATTR_TESTED), newValue);
         changedValues.put(QueryResult.createNodeResult(changedNode), newValue);
         final NodeUpdateData<ImmutableNode> updateData = new NodeUpdateData<>(changedValues, null, null, null);
 
         when(resolver.resolveUpdateKey(NodeStructureHelper.ROOT_PERSONAE_TREE, KEY, this, model.getNodeHandler())).thenReturn(updateData);
 
         model.setProperty(KEY, this, resolver);
         final ImmutableNode node = nodeForKey(model, nodeKey);
         assertEquals(newValue, node.getAttributes().get(NodeStructureHelper.ATTR_TESTED));
         assertEquals(newValue, node.getValue());
     }
 
     /**
      * Tests whether setProperty() can handle nodes to be cleared.
      */
     @Test
     void testSetPropertyClearValues() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
         final String nodeKey = "Ariel/The Tempest/" + NodeStructureHelper.ELEM_ORG_VALUE;
         final NodeUpdateData<ImmutableNode> updateData = new NodeUpdateData<>(null, null,
             Collections.singletonList(QueryResult.createNodeResult(nodeForKey(model, nodeKey))), null);
 
         when(resolver.resolveUpdateKey(NodeStructureHelper.ROOT_PERSONAE_TREE, KEY, this, model.getNodeHandler())).thenReturn(updateData);
 
         model.setProperty(KEY, this, resolver);
         final ImmutableNode node = nodeForKey(model, nodeKey);
         assertNull(node.getValue());
     }
 
     /**
      * Tests whether setProperty() can handle newly added values.
      */
     @Test
     void testSetPropertyNewValues() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final NodeAddData<ImmutableNode> addData = new NodeAddData<>(nodeForKey(ROOT_AUTHORS_TREE, "Homer"), "work", false, null);
         final NodeUpdateData<ImmutableNode> updateData = new NodeUpdateData<>(null, Collections.<Object>singleton("Odyssee"), null, KEY);
         final InMemoryNodeModel model = new InMemoryNodeModel(ROOT_AUTHORS_TREE);
 
         when(resolver.resolveUpdateKey(ROOT_AUTHORS_TREE, KEY, this, model.getNodeHandler())).thenReturn(updateData);
         when(resolver.resolveAddKey(ROOT_AUTHORS_TREE, KEY, model.getNodeHandler())).thenReturn(addData);
 
         model.setProperty(KEY, this, resolver);
         final ImmutableNode node = nodeForKey(model, "Homer/work");
         assertEquals("Odyssee", node.getValue());
         assertNotNull(nodeForKey(model, "Homer/Ilias/Hektor"));
     }
 
     /**
      * Tests a set property operation which is a no-op.
      */
     @Test
     void testSetPropertyNoChanges() {
         final NodeKeyResolver<ImmutableNode> resolver = createResolver();
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
 
         when(resolver.resolveUpdateKey(NodeStructureHelper.ROOT_PERSONAE_TREE, KEY, this, model.getNodeHandler()))
                 .thenReturn(new NodeUpdateData<>(null, null, null, null));
 
         model.setProperty(KEY, this, resolver);
         assertSame(NodeStructureHelper.ROOT_PERSONAE_TREE, model.getRootNode());
     }
 
     /**
      * Tests whether a new root node can be set.
      */
     @Test
     void testSetRoot() {
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
         model.setRootNode(NodeStructureHelper.ROOT_AUTHORS_TREE);
         assertSame(NodeStructureHelper.ROOT_AUTHORS_TREE, model.getRootNode());
         final ImmutableNode node = nodeForKey(model, "Homer/Ilias");
         assertEquals(nodeForKey(model, "Homer"), model.getNodeHandler().getParent(node));
     }
 
     /**
      * Tests whether the root node can be set to null.
      */
     @Test
     void testSetRootNull() {
         final InMemoryNodeModel model = new InMemoryNodeModel(NodeStructureHelper.ROOT_PERSONAE_TREE);
         model.setRootNode(null);
         final ImmutableNode rootNode = model.getRootNode();
         assertTrue(rootNode.getChildren().isEmpty());
     }
 }