diff --git a/phpBB/includes/lock/db.php b/phpBB/includes/lock/db.php
index ccdaed0b28..5cc0821aa0 100644
--- a/phpBB/includes/lock/db.php
+++ b/phpBB/includes/lock/db.php
@@ -116,6 +116,17 @@ class phpbb_lock_db
 		return $this->locked;
 	}
 
+	/**
+	* Does this process own the lock?
+	*
+	* @return	bool			true if lock is owned
+	*							false otherwise
+	*/
+	public function owns_lock()
+	{
+		return (bool) $this->locked;
+	}
+
 	/**
 	* Releases the lock.
 	*
diff --git a/phpBB/includes/lock/flock.php b/phpBB/includes/lock/flock.php
index 97bc7dd2b9..17de0847c0 100644
--- a/phpBB/includes/lock/flock.php
+++ b/phpBB/includes/lock/flock.php
@@ -110,6 +110,17 @@ class phpbb_lock_flock
 		return (bool) $this->lock_fp;
 	}
 
+	/**
+	* Does this process own the lock?
+	*
+	* @return	bool			true if lock is owned
+	*							false otherwise
+	*/
+	public function owns_lock()
+	{
+		return (bool) $this->lock_fp;
+	}
+
 	/**
 	* Releases the lock.
 	*
diff --git a/phpBB/includes/tree/interface.php b/phpBB/includes/tree/interface.php
new file mode 100644
index 0000000000..cc8aab2115
--- /dev/null
+++ b/phpBB/includes/tree/interface.php
@@ -0,0 +1,122 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+interface phpbb_tree_interface
+{
+	/**
+	* Inserts an item into the database table and into the tree.
+	*
+	* @param array	$item	The item to be added
+	* @return array Array with item data as set in the database
+	*/
+	public function insert(array $additional_data);
+
+	/**
+	* Delete an item from the tree and from the database table
+	*
+	* Also deletes the subtree from the tree and from the database table
+	*
+	* @param int	$item_id	The item to be deleted
+	* @return array		Item ids that have been deleted
+	*/
+	public function delete($item_id);
+
+	/**
+	* Move an item by a given delta
+	*
+	* An item is only moved up/down within the same parent. If the delta is
+	* larger then the number of children, the item is moved to the top/bottom
+	* of the list of children within this parent.
+	*
+	* @param int	$item_id	The item to be moved
+	* @param int	$delta		Number of steps to move this item, < 0 => down, > 0 => up
+	* @return bool True if the item was moved
+	*/
+	public function move($item_id, $delta);
+
+	/**
+	* Move an item down by 1
+	*
+	* @param int	$item_id	The item to be moved
+	* @return bool True if the item was moved
+	*/
+	public function move_down($item_id);
+
+	/**
+	* Move an item up by 1
+	*
+	* @param int	$item_id	The item to be moved
+	* @return bool True if the item was moved
+	*/
+	public function move_up($item_id);
+
+	/**
+	* Moves all children of one item to another item
+	*
+	* If the new parent already has children, the new children are appended
+	* to the list.
+	*
+	* @param int	$current_parent_id	The current parent item
+	* @param int	$new_parent_id		The new parent item
+	* @return bool True if any items where moved
+	*/
+	public function move_children($current_parent_id, $new_parent_id);
+
+	/**
+	* Change parent item
+	*
+	* Moves the item to the bottom of the new parent's list of children
+	*
+	* @param int	$item_id			The item to be moved
+	* @param int	$new_parent_id		The new parent item
+	* @return bool True if the parent was set successfully
+	*/
+	public function change_parent($item_id, $new_parent_id);
+
+	/**
+	* Get all items that are either ancestors or descendants of the item
+	*
+	* @param int		$item_id		Id of the item to retrieve the ancestors/descendants from
+	* @param bool		$order_asc		Order the items ascendingly (most outer ancestor first)
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_path_and_subtree_data($item_id, $order_asc, $include_item);
+
+	/**
+	* Get all of the item's ancestors
+	*
+	* @param int		$item_id		Id of the item to retrieve the ancestors from
+	* @param bool		$order_asc		Order the items ascendingly (most outer ancestor first)
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_path_data($item_id, $order_asc, $include_item);
+
+	/**
+	* Get all of the item's descendants
+	*
+	* @param int		$item_id		Id of the item to retrieve the descendants from
+	* @param bool		$order_asc		Order the items ascendingly
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_subtree_data($item_id, $order_asc, $include_item);
+}
diff --git a/phpBB/includes/tree/nestedset.php b/phpBB/includes/tree/nestedset.php
new file mode 100644
index 0000000000..4d851a87a8
--- /dev/null
+++ b/phpBB/includes/tree/nestedset.php
@@ -0,0 +1,850 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+abstract class phpbb_tree_nestedset implements phpbb_tree_interface
+{
+	/** @var phpbb_db_driver */
+	protected $db;
+
+	/** @var phpbb_lock_db */
+	protected $lock;
+
+	/** @var string */
+	protected $table_name;
+
+	/**
+	* Prefix for the language keys returned by exceptions
+	* @var string
+	*/
+	protected $message_prefix = '';
+
+	/**
+	* Column names in the table
+	* @var string
+	*/
+	protected $column_item_id = 'item_id';
+	protected $column_left_id = 'left_id';
+	protected $column_right_id = 'right_id';
+	protected $column_parent_id = 'parent_id';
+	protected $column_item_parents = 'item_parents';
+
+	/**
+	* Additional SQL restrictions
+	* Allows to have multiple nested sets in one table
+	* @var string
+	*/
+	protected $sql_where = '';
+
+	/**
+	* List of item properties to be cached in the item_parents column
+	* @var array
+	*/
+	protected $item_basic_data = array('*');
+
+	/**
+	* Construct
+	*
+	* @param phpbb_db_driver	$db		Database connection
+	* @param phpbb_lock_db		$lock	Lock class used to lock the table when moving forums around
+	* @param string			$table_name			Table name
+	* @param string			$message_prefix		Prefix for the messages thrown by exceptions
+	* @param string			$sql_where			Additional SQL restrictions for the queries
+	* @param array			$item_basic_data	Array with basic item data that is stored in item_parents
+	* @param array			$columns			Array with column names to overwrite
+	*/
+	public function __construct(phpbb_db_driver $db, phpbb_lock_db $lock, $table_name, $message_prefix = '', $sql_where = '', $item_basic_data = array(), $columns = array())
+	{
+		$this->db = $db;
+		$this->lock = $lock;
+
+		$this->table_name = $table_name;
+		$this->message_prefix = $message_prefix;
+		$this->sql_where = $sql_where;
+		$this->item_basic_data = (!empty($item_basic_data)) ? $item_basic_data : array('*');
+
+		if (!empty($columns))
+		{
+			foreach ($columns as $column => $name)
+			{
+				$column_name = 'column_' . $column;
+				$this->$column_name = $name;
+			}
+		}
+	}
+
+	/**
+	* Returns additional sql where restrictions
+	*
+	* @param string		$operator		SQL operator that needs to be prepended to sql_where,
+	*									if it is not empty.
+	* @param string		$column_prefix	Prefix that needs to be prepended to column names
+	* @return string		Returns additional where statements to narrow down the tree,
+	*						prefixed with operator and prepended column_prefix to column names
+	*/
+	public function get_sql_where($operator = 'AND', $column_prefix = '')
+	{
+		return (!$this->sql_where) ? '' : $operator . ' ' . sprintf($this->sql_where, $column_prefix);
+	}
+
+	/**
+	* Acquires a lock on the item table
+	*
+	* @return bool	True if the lock was acquired, false if it has been acquired previously
+	*
+	* @throws RuntimeException If the lock could not be acquired
+	*/
+	protected function acquire_lock()
+	{
+		if ($this->lock->owns_lock())
+		{
+			return false;
+		}
+
+		if (!$this->lock->acquire())
+		{
+			throw new RuntimeException($this->message_prefix . 'LOCK_FAILED_ACQUIRE');
+		}
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function insert(array $additional_data)
+	{
+		$item_data = $this->reset_nestedset_values($additional_data);
+
+		$sql = 'INSERT INTO ' . $this->table_name . ' ' . $this->db->sql_build_array('INSERT', $item_data);
+		$this->db->sql_query($sql);
+
+		$item_data[$this->column_item_id] = (int) $this->db->sql_nextid();
+
+		return array_merge($item_data, $this->add_item_to_nestedset($item_data[$this->column_item_id]));
+	}
+
+	/**
+	* Add an item which already has a database row at the end of the tree
+	*
+	* @param int	$item_id	The item to be added
+	* @return array		Array with updated data, if the item was added successfully
+	*					Empty array otherwise
+	*/
+	protected function add_item_to_nestedset($item_id)
+	{
+		$sql = 'SELECT MAX(' . $this->column_right_id . ') AS ' . $this->column_right_id . '
+			FROM ' . $this->table_name . '
+			' . $this->get_sql_where('WHERE');
+		$result = $this->db->sql_query($sql);
+		$current_max_right_id = (int) $this->db->sql_fetchfield($this->column_right_id);
+		$this->db->sql_freeresult($result);
+
+		$update_item_data = array(
+			$this->column_parent_id		=> 0,
+			$this->column_left_id		=> $current_max_right_id + 1,
+			$this->column_right_id		=> $current_max_right_id + 2,
+			$this->column_item_parents	=> '',
+		);
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->db->sql_build_array('UPDATE', $update_item_data) . '
+			WHERE ' . $this->column_item_id . ' = ' . (int) $item_id . '
+				AND ' . $this->column_parent_id . ' = 0
+				AND ' . $this->column_left_id . ' = 0
+				AND ' . $this->column_right_id . ' = 0';
+		$this->db->sql_query($sql);
+
+		return ($this->db->sql_affectedrows() == 1) ? $update_item_data : array();
+	}
+
+	/**
+	* Remove an item from the tree without deleting it from the database
+	*
+	* Also removes all subitems from the tree without deleting them from the database either
+	*
+	* @param int	$item_id	The item to be deleted
+	* @return array		Item ids that have been removed
+	*/
+	protected function remove_item_from_nestedset($item_id)
+	{
+		$item_id = (int) $item_id;
+		if (!$item_id)
+		{
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$items = $this->get_subtree_data($item_id);
+		$item_ids = array_keys($items);
+
+		if (empty($items) || !isset($items[$item_id]))
+		{
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$this->remove_subset($item_ids, $items[$item_id]);
+
+		return $item_ids;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function delete($item_id)
+	{
+		$removed_items = $this->remove_item_from_nestedset($item_id);
+
+		$sql = 'DELETE FROM ' . $this->table_name . '
+			WHERE ' . $this->db->sql_in_set($this->column_item_id, $removed_items) . '
+			' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		return $removed_items;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move($item_id, $delta)
+	{
+		if ($delta == 0)
+		{
+			return false;
+		}
+
+		$this->acquire_lock();
+
+		$action = ($delta > 0) ? 'move_up' : 'move_down';
+		$delta = abs($delta);
+
+		// Keep $this->get_sql_where() here, to ensure we are in the right tree.
+		$sql = 'SELECT *
+			FROM ' . $this->table_name . '
+			WHERE ' . $this->column_item_id . ' = ' . (int) $item_id . '
+				' . $this->get_sql_where();
+		$result = $this->db->sql_query_limit($sql, $delta);
+		$item = $this->db->sql_fetchrow($result);
+		$this->db->sql_freeresult($result);
+
+		if (!$item)
+		{
+			$this->lock->release();
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		/**
+		* Fetch all the siblings between the item's current spot
+		* and where we want to move it to. If there are less than $delta
+		* siblings between the current spot and the target then the
+		* item will move as far as possible
+		*/
+		$sql = "SELECT {$this->column_item_id}, {$this->column_parent_id}, {$this->column_left_id}, {$this->column_right_id}, {$this->column_item_parents}
+			FROM " . $this->table_name . '
+			WHERE ' . $this->column_parent_id . ' = ' . (int) $item[$this->column_parent_id] . '
+				' . $this->get_sql_where() . '
+				AND ';
+
+		if ($action == 'move_up')
+		{
+			$sql .= $this->column_right_id . ' < ' . (int) $item[$this->column_right_id] . ' ORDER BY ' . $this->column_right_id . ' DESC';
+		}
+		else
+		{
+			$sql .= $this->column_left_id . ' > ' . (int) $item[$this->column_left_id] . ' ORDER BY ' . $this->column_left_id . ' ASC';
+		}
+
+		$result = $this->db->sql_query_limit($sql, $delta);
+
+		$target = false;
+		while ($row = $this->db->sql_fetchrow($result))
+		{
+			$target = $row;
+		}
+		$this->db->sql_freeresult($result);
+
+		if (!$target)
+		{
+			$this->lock->release();
+			// The item is already on top or bottom
+			return false;
+		}
+
+		/**
+		* $left_id and $right_id define the scope of the items that are affected by the move.
+		* $diff_up and $diff_down are the values to substract or add to each item's left_id
+		* and right_id in order to move them up or down.
+		* $move_up_left and $move_up_right define the scope of the items that are moving
+		* up. Other items in the scope of ($left_id, $right_id) are considered to move down.
+		*/
+		if ($action == 'move_up')
+		{
+			$left_id = (int) $target[$this->column_left_id];
+			$right_id = (int) $item[$this->column_right_id];
+
+			$diff_up = (int) $item[$this->column_left_id] - (int) $target[$this->column_left_id];
+			$diff_down = (int) $item[$this->column_right_id] + 1 - (int) $item[$this->column_left_id];
+
+			$move_up_left = (int) $item[$this->column_left_id];
+			$move_up_right = (int) $item[$this->column_right_id];
+		}
+		else
+		{
+			$left_id = (int) $item[$this->column_left_id];
+			$right_id = (int) $target[$this->column_right_id];
+
+			$diff_up = (int) $item[$this->column_right_id] + 1 - (int) $item[$this->column_left_id];
+			$diff_down = (int) $target[$this->column_right_id] - (int) $item[$this->column_right_id];
+
+			$move_up_left = (int) $item[$this->column_right_id] + 1;
+			$move_up_right = (int) $target[$this->column_right_id];
+		}
+
+		// Now do the dirty job
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $this->column_left_id . ' + CASE
+				WHEN ' . $this->column_left_id . " BETWEEN {$move_up_left} AND {$move_up_right} THEN -{$diff_up}
+				ELSE {$diff_down}
+			END,
+			" . $this->column_right_id . ' = ' . $this->column_right_id . ' + CASE
+				WHEN ' . $this->column_right_id . " BETWEEN {$move_up_left} AND {$move_up_right} THEN -{$diff_up}
+				ELSE {$diff_down}
+			END
+			WHERE
+				" . $this->column_left_id . " BETWEEN {$left_id} AND {$right_id}
+				AND " . $this->column_right_id . " BETWEEN {$left_id} AND {$right_id}
+				" . $this->get_sql_where();
+		$this->db->sql_query($sql);
+
+		$this->lock->release();
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move_down($item_id)
+	{
+		return $this->move($item_id, -1);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move_up($item_id)
+	{
+		return $this->move($item_id, 1);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function move_children($current_parent_id, $new_parent_id)
+	{
+		$current_parent_id = (int) $current_parent_id;
+		$new_parent_id = (int) $new_parent_id;
+
+		if ($current_parent_id == $new_parent_id)
+		{
+			return false;
+		}
+
+		if (!$current_parent_id)
+		{
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$this->acquire_lock();
+
+		$item_data = $this->get_subtree_data($current_parent_id);
+		if (!isset($item_data[$current_parent_id]))
+		{
+			$this->lock->release();
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$current_parent = $item_data[$current_parent_id];
+		unset($item_data[$current_parent_id]);
+		$move_items = array_keys($item_data);
+
+		if (($current_parent[$this->column_right_id] - $current_parent[$this->column_left_id]) <= 1)
+		{
+			$this->lock->release();
+			return false;
+		}
+
+		if (in_array($new_parent_id, $move_items))
+		{
+			$this->lock->release();
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+		}
+
+		$diff = sizeof($move_items) * 2;
+		$sql_exclude_moved_items = $this->db->sql_in_set($this->column_item_id, $move_items, true);
+
+		$this->db->sql_transaction('begin');
+
+		$this->remove_subset($move_items, $current_parent, false, true);
+
+		if ($new_parent_id)
+		{
+			// Retrieve new-parent again, it may have been changed...
+			$sql = 'SELECT *
+				FROM ' . $this->table_name . '
+				WHERE ' . $this->column_item_id . ' = ' . $new_parent_id;
+			$result = $this->db->sql_query($sql);
+			$new_parent = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			if (!$new_parent)
+			{
+				$this->db->sql_transaction('rollback');
+				$this->lock->release();
+				throw new OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+			}
+
+			$new_right_id = $this->prepare_adding_subset($move_items, $new_parent, true);
+
+			if ($new_right_id > $current_parent[$this->column_right_id])
+			{
+				$diff = ' + ' . ($new_right_id - $current_parent[$this->column_right_id]);
+			}
+			else
+			{
+				$diff = ' - ' . abs($new_right_id - $current_parent[$this->column_right_id]);
+			}
+		}
+		else
+		{
+			$sql = 'SELECT MAX(' . $this->column_right_id . ') AS ' . $this->column_right_id . '
+				FROM ' . $this->table_name . '
+				WHERE ' . $sql_exclude_moved_items . '
+					' . $this->get_sql_where('AND');
+			$result = $this->db->sql_query($sql);
+			$row = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			$diff = ' + ' . ($row[$this->column_right_id] - $current_parent[$this->column_left_id]);
+		}
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $this->column_left_id . $diff . ',
+				' . $this->column_right_id . ' = ' . $this->column_right_id . $diff . ',
+				' . $this->column_parent_id . ' = ' . $this->db->sql_case($this->column_parent_id . ' = ' . $current_parent_id, $new_parent_id, $this->column_parent_id) . ',
+				' . $this->column_item_parents . " = ''
+			WHERE " . $this->db->sql_in_set($this->column_item_id, $move_items) . '
+				' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		$this->db->sql_transaction('commit');
+		$this->lock->release();
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function change_parent($item_id, $new_parent_id)
+	{
+		$item_id = (int) $item_id;
+		$new_parent_id = (int) $new_parent_id;
+
+		if ($item_id == $new_parent_id)
+		{
+			return false;
+		}
+
+		if (!$item_id)
+		{
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$this->acquire_lock();
+
+		$item_data = $this->get_subtree_data($item_id);
+		if (!isset($item_data[$item_id]))
+		{
+			$this->lock->release();
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_ITEM');
+		}
+
+		$item = $item_data[$item_id];
+		$move_items = array_keys($item_data);
+
+		if (in_array($new_parent_id, $move_items))
+		{
+			$this->lock->release();
+			throw new OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+		}
+
+		$diff = sizeof($move_items) * 2;
+		$sql_exclude_moved_items = $this->db->sql_in_set($this->column_item_id, $move_items, true);
+
+		$this->db->sql_transaction('begin');
+
+		$this->remove_subset($move_items, $item, false, true);
+
+		if ($new_parent_id)
+		{
+			// Retrieve new-parent again, it may have been changed...
+			$sql = 'SELECT *
+				FROM ' . $this->table_name . '
+				WHERE ' . $this->column_item_id . ' = ' . $new_parent_id;
+			$result = $this->db->sql_query($sql);
+			$new_parent = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			if (!$new_parent)
+			{
+				$this->db->sql_transaction('rollback');
+				$this->lock->release();
+				throw new OutOfBoundsException($this->message_prefix . 'INVALID_PARENT');
+			}
+
+			$new_right_id = $this->prepare_adding_subset($move_items, $new_parent, true);
+
+			if ($new_right_id > (int) $item[$this->column_right_id])
+			{
+				$diff = ' + ' . ($new_right_id - (int) $item[$this->column_right_id] - 1);
+			}
+			else
+			{
+				$diff = ' - ' . abs($new_right_id - (int) $item[$this->column_right_id] - 1);
+			}
+		}
+		else
+		{
+			$sql = 'SELECT MAX(' . $this->column_right_id . ') AS ' . $this->column_right_id . '
+				FROM ' . $this->table_name . '
+				WHERE ' . $sql_exclude_moved_items . '
+					' . $this->get_sql_where('AND');
+			$result = $this->db->sql_query($sql);
+			$row = $this->db->sql_fetchrow($result);
+			$this->db->sql_freeresult($result);
+
+			$diff = ' + ' . ($row[$this->column_right_id] - (int) $item[$this->column_left_id] + 1);
+		}
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $this->column_left_id . $diff . ',
+				' . $this->column_right_id . ' = ' . $this->column_right_id . $diff . ',
+				' . $this->column_parent_id . ' = ' . $this->db->sql_case($this->column_item_id . ' = ' . $item_id, $new_parent_id, $this->column_parent_id) . ',
+				' . $this->column_item_parents . " = ''
+			WHERE " . $this->db->sql_in_set($this->column_item_id, $move_items) . '
+				' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		$this->db->sql_transaction('commit');
+		$this->lock->release();
+
+		return true;
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_path_and_subtree_data($item_id, $order_asc = true, $include_item = true)
+	{
+		$condition = 'i2.' . $this->column_left_id . ' BETWEEN i1.' . $this->column_left_id . ' AND i1.' . $this->column_right_id . '
+			OR i1.' . $this->column_left_id . ' BETWEEN i2.' . $this->column_left_id . ' AND i2.' . $this->column_right_id;
+
+		return $this->get_set_of_nodes_data($item_id, $condition, $order_asc, $include_item);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_path_data($item_id, $order_asc = true, $include_item = true)
+	{
+		$condition = 'i1.' . $this->column_left_id . ' BETWEEN i2.' . $this->column_left_id . ' AND i2.' . $this->column_right_id . '';
+
+		return $this->get_set_of_nodes_data($item_id, $condition, $order_asc, $include_item);
+	}
+
+	/**
+	* @inheritdoc
+	*/
+	public function get_subtree_data($item_id, $order_asc = true, $include_item = true)
+	{
+		$condition = 'i2.' . $this->column_left_id . ' BETWEEN i1.' . $this->column_left_id . ' AND i1.' . $this->column_right_id . '';
+
+		return $this->get_set_of_nodes_data($item_id, $condition, $order_asc, $include_item);
+	}
+
+	/**
+	* Get items that are related to the given item by the condition
+	*
+	* @param int		$item_id		Id of the item to retrieve the node set from
+	* @param string		$condition		Query string restricting the item list
+	* @param bool		$order_asc		Order the items ascending by their left_id
+	* @param bool		$include_item	Should the item matching the given item id be included in the list as well
+	* @return array			Array of items (containing all columns from the item table)
+	*							ID => Item data
+	*/
+	protected function get_set_of_nodes_data($item_id, $condition, $order_asc = true, $include_item = true)
+	{
+		$rows = array();
+
+		$sql = 'SELECT i2.*
+			FROM ' . $this->table_name . ' i1
+			LEFT JOIN ' . $this->table_name . " i2
+				ON (($condition) " . $this->get_sql_where('AND', 'i2.') . ')
+			WHERE i1.' . $this->column_item_id . ' = ' . (int) $item_id . '
+				' . $this->get_sql_where('AND', 'i1.') . '
+			ORDER BY i2.' . $this->column_left_id . ' ' . ($order_asc ? 'ASC' : 'DESC');
+		$result = $this->db->sql_query($sql);
+
+		while ($row = $this->db->sql_fetchrow($result))
+		{
+			if (!$include_item && $item_id == $row[$this->column_item_id])
+			{
+				continue;
+			}
+
+			$rows[(int) $row[$this->column_item_id]] = $row;
+		}
+		$this->db->sql_freeresult($result);
+
+		return $rows;
+	}
+
+	/**
+	* Get basic data of all parent items
+	*
+	* Basic data is defined in the $item_basic_data property.
+	* Data is cached in the item_parents column in the item table
+	*
+	* @param array	$item		The item to get the path from
+	* @return array			Array of items (containing basic columns from the item table)
+	*							ID => Item data
+	*/
+	public function get_path_basic_data(array $item)
+	{
+		$parents = array();
+		if ($item[$this->column_parent_id])
+		{
+			if (!$item[$this->column_item_parents])
+			{
+				$sql = 'SELECT ' . implode(', ', $this->item_basic_data) . '
+					FROM ' . $this->table_name . '
+					WHERE ' . $this->column_left_id . ' < ' . (int) $item[$this->column_left_id] . '
+						AND ' . $this->column_right_id . ' > ' . (int) $item[$this->column_right_id] . '
+						' . $this->get_sql_where('AND') . '
+					ORDER BY ' . $this->column_left_id . ' ASC';
+				$result = $this->db->sql_query($sql);
+
+				while ($row = $this->db->sql_fetchrow($result))
+				{
+					$parents[$row[$this->column_item_id]] = $row;
+				}
+				$this->db->sql_freeresult($result);
+
+				$item_parents = serialize($parents);
+
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->column_item_parents . " = '" . $this->db->sql_escape($item_parents) . "'
+					WHERE " . $this->column_parent_id . ' = ' . (int) $item[$this->column_parent_id];
+				$this->db->sql_query($sql);
+			}
+			else
+			{
+				$parents = unserialize($item[$this->column_item_parents]);
+			}
+		}
+
+		return $parents;
+	}
+
+	/**
+	* Remove a subset from the nested set
+	*
+	* @param array	$subset_items		Subset of items to remove
+	* @param array	$bounding_item		Item containing the right bound of the subset
+	* @param bool	$set_subset_zero	Should the parent, left and right id of the items be set to 0, or kept unchanged?
+	*									In case of removing an item from the tree, we should the values to 0
+	*									In case of moving an item, we shouldkeep the original values, in order to allow "+ diff" later
+	* @return	null
+	*/
+	protected function remove_subset(array $subset_items, array $bounding_item, $set_subset_zero = true)
+	{
+		$acquired_new_lock = $this->acquire_lock();
+
+		$diff = sizeof($subset_items) * 2;
+		$sql_subset_items = $this->db->sql_in_set($this->column_item_id, $subset_items);
+		$sql_not_subset_items = $this->db->sql_in_set($this->column_item_id, $subset_items, true);
+
+		$sql_is_parent = $this->column_left_id . ' <= ' . (int) $bounding_item[$this->column_right_id] . '
+			AND ' . $this->column_right_id . ' >= ' . (int) $bounding_item[$this->column_right_id];
+
+		$sql_is_right = $this->column_left_id . ' > ' . (int) $bounding_item[$this->column_right_id];
+
+		$set_left_id = $this->db->sql_case($sql_is_right, $this->column_left_id . ' - ' . $diff, $this->column_left_id);
+		$set_right_id = $this->db->sql_case($sql_is_parent . ' OR ' . $sql_is_right, $this->column_right_id . ' - ' . $diff, $this->column_right_id);
+
+		if ($set_subset_zero)
+		{
+			$set_left_id = $this->db->sql_case($sql_subset_items, 0, $set_left_id);
+			$set_right_id = $this->db->sql_case($sql_subset_items, 0, $set_right_id);
+		}
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . (($set_subset_zero) ? $this->column_parent_id . ' = ' . $this->db->sql_case($sql_subset_items, 0, $this->column_parent_id) . ',' : '') . '
+				' . $this->column_left_id . ' = ' . $set_left_id . ',
+				' . $this->column_right_id . ' = ' . $set_right_id . '
+			' . ((!$set_subset_zero) ? ' WHERE ' . $sql_not_subset_items . ' ' . $this->get_sql_where('AND') : $this->get_sql_where('WHERE'));
+		$this->db->sql_query($sql);
+
+		if ($acquired_new_lock)
+		{
+			$this->lock->release();
+		}
+	}
+
+	/**
+	* Prepare adding a subset to the nested set
+	*
+	* @param array	$subset_items		Subset of items to add
+	* @param array	$new_parent	Item containing the right bound of the new parent
+	* @return	int		New right id of the parent item
+	*/
+	protected function prepare_adding_subset(array $subset_items, array $new_parent)
+	{
+		$diff = sizeof($subset_items) * 2;
+		$sql_not_subset_items = $this->db->sql_in_set($this->column_item_id, $subset_items, true);
+
+		$set_left_id = $this->db->sql_case($this->column_left_id . ' > ' . (int) $new_parent[$this->column_right_id], $this->column_left_id . ' + ' . $diff, $this->column_left_id);
+		$set_right_id = $this->db->sql_case($this->column_right_id . ' >= ' . (int) $new_parent[$this->column_right_id], $this->column_right_id . ' + ' . $diff, $this->column_right_id);
+
+		$sql = 'UPDATE ' . $this->table_name . '
+			SET ' . $this->column_left_id . ' = ' . $set_left_id . ',
+				' . $this->column_right_id . ' = ' . $set_right_id . '
+			WHERE ' . $sql_not_subset_items . '
+				' . $this->get_sql_where('AND');
+		$this->db->sql_query($sql);
+
+		return $new_parent[$this->column_right_id] + $diff;
+	}
+
+	/**
+	* Resets values required for the nested set system
+	*
+	* @param array	$item		Original item data
+	* @return	array		Original item data + nested set defaults
+	*/
+	protected function reset_nestedset_values(array $item)
+	{
+		$item_data = array_merge($item, array(
+			$this->column_parent_id		=> 0,
+			$this->column_left_id		=> 0,
+			$this->column_right_id		=> 0,
+			$this->column_item_parents	=> '',
+		));
+
+		unset($item_data[$this->column_item_id]);
+
+		return $item_data;
+	}
+
+	/**
+	* Regenerate left/right ids from parent/child relationship
+	*
+	* This method regenerates the left/right ids for the tree based on
+	* the parent/child relations. This function executes three queries per
+	* item, so it should only be called, when the set has one of the following
+	* problems:
+	*	- The set has a duplicated value inside the left/right id chain
+	*	- The set has a missing value inside the left/right id chain
+	*	- The set has items that do not have a left/right id set
+	*
+	* When regenerating the items, the items are sorted by parent id and their
+	* current left id, so the current child/parent relationships are kept
+	* and running the function on a working set will not change the order.
+	*
+	* @param int	$new_id		First left_id to be used (should start with 1)
+	* @param int	$parent_id	parent_id of the current set (default = 0)
+	* @param bool	$reset_ids	Should we reset all left_id/right_id on the first call?
+	* @return	int		$new_id		The next left_id/right_id that should be used
+	*/
+	public function regenerate_left_right_ids($new_id, $parent_id = 0, $reset_ids = false)
+	{
+		if ($acquired_new_lock = $this->acquire_lock())
+		{
+			$this->db->sql_transaction('begin');
+
+			if (!$reset_ids)
+			{
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->column_item_parents . " = ''
+					" . $this->get_sql_where('WHERE');
+				$this->db->sql_query($sql);
+			}
+		}
+
+		if ($reset_ids)
+		{
+			$sql = 'UPDATE ' . $this->table_name . '
+				SET ' . $this->db->sql_build_array('UPDATE', array(
+					$this->column_left_id		=> 0,
+					$this->column_right_id		=> 0,
+					$this->column_item_parents	=> '',
+				)) . '
+				' . $this->get_sql_where('WHERE');
+			$this->db->sql_query($sql);
+		}
+
+		$sql = 'SELECT *
+			FROM ' . $this->table_name . '
+			WHERE ' . $this->column_parent_id . ' = ' . (int) $parent_id . '
+				' . $this->get_sql_where('AND') . '
+			ORDER BY ' . $this->column_left_id . ', ' . $this->column_item_id . ' ASC';
+		$result = $this->db->sql_query($sql);
+		while ($row = $this->db->sql_fetchrow($result))
+		{
+			// First we update the left_id for this module
+			if ($row[$this->column_left_id] != $new_id)
+			{
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->db->sql_build_array('UPDATE', array($this->column_left_id => $new_id)) . '
+					WHERE ' . $this->column_item_id . ' = ' . (int) $row[$this->column_item_id];
+				$this->db->sql_query($sql);
+			}
+			$new_id++;
+
+			// Then we go through any children and update their left/right id's
+			$new_id = $this->regenerate_left_right_ids($new_id, $row[$this->column_item_id]);
+
+			// Then we come back and update the right_id for this module
+			if ($row[$this->column_right_id] != $new_id)
+			{
+				$sql = 'UPDATE ' . $this->table_name . '
+					SET ' . $this->db->sql_build_array('UPDATE', array($this->column_right_id => $new_id)) . '
+					WHERE ' . $this->column_item_id . ' = ' . (int) $row[$this->column_item_id];
+				$this->db->sql_query($sql);
+			}
+			$new_id++;
+		}
+		$this->db->sql_freeresult($result);
+
+		if ($acquired_new_lock)
+		{
+			$this->db->sql_transaction('commit');
+			$this->lock->release();
+		}
+
+		return $new_id;
+	}
+}
diff --git a/phpBB/includes/tree/nestedset_forum.php b/phpBB/includes/tree/nestedset_forum.php
new file mode 100644
index 0000000000..ff09ef55d0
--- /dev/null
+++ b/phpBB/includes/tree/nestedset_forum.php
@@ -0,0 +1,46 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+class phpbb_tree_nestedset_forum extends phpbb_tree_nestedset
+{
+	/**
+	* Construct
+	*
+	* @param phpbb_db_driver	$db		Database connection
+	* @param phpbb_lock_db		$lock	Lock class used to lock the table when moving forums around
+	* @param string				$table_name		Table name
+	*/
+	public function __construct(phpbb_db_driver $db, phpbb_lock_db $lock, $table_name)
+	{
+		parent::__construct(
+			$db,
+			$lock,
+			$table_name,
+			'FORUM_NESTEDSET_',
+			'',
+			array(
+				'forum_id',
+				'forum_name',
+				'forum_type',
+			),
+			array(
+				'item_id'		=> 'forum_id',
+				'item_parents'	=> 'forum_parents',
+			)
+		);
+	}
+}
diff --git a/tests/lock/db_test.php b/tests/lock/db_test.php
index f7b1557a0c..de7a23fd05 100644
--- a/tests/lock/db_test.php
+++ b/tests/lock/db_test.php
@@ -32,13 +32,18 @@ class phpbb_lock_db_test extends phpbb_database_test_case
 
 	public function test_new_lock()
 	{
+		$this->assertFalse($this->lock->owns_lock());
+
 		$this->assertTrue($this->lock->acquire());
+		$this->assertTrue($this->lock->owns_lock());
 		$this->assertTrue(isset($this->config['test_lock']), 'Lock was created');
 
 		$lock2 = new phpbb_lock_db('test_lock', $this->config, $this->db);
 		$this->assertFalse($lock2->acquire());
+		$this->assertFalse($lock2->owns_lock());
 
 		$this->lock->release();
+		$this->assertFalse($this->lock->owns_lock());
 		$this->assertEquals('0', $this->config['test_lock'], 'Lock was released');
 	}
 
@@ -50,31 +55,40 @@ class phpbb_lock_db_test extends phpbb_database_test_case
 
 	public function test_double_lock()
 	{
+		$this->assertFalse($this->lock->owns_lock());
+
 		$this->assertTrue($this->lock->acquire());
+		$this->assertTrue($this->lock->owns_lock());
 		$this->assertTrue(isset($this->config['test_lock']), 'Lock was created');
 
 		$value = $this->config['test_lock'];
 
 		$this->assertFalse($this->lock->acquire());
+		$this->assertTrue($this->lock->owns_lock());
 		$this->assertEquals($value, $this->config['test_lock'], 'Second lock failed');
 
 		$this->lock->release();
+		$this->assertFalse($this->lock->owns_lock());
 		$this->assertEquals('0', $this->config['test_lock'], 'Lock was released');
 	}
 
 	public function test_double_unlock()
 	{
 		$this->assertTrue($this->lock->acquire());
+		$this->assertTrue($this->lock->owns_lock());
 		$this->assertFalse(empty($this->config['test_lock']), 'First lock is acquired');
 
 		$this->lock->release();
+		$this->assertFalse($this->lock->owns_lock());
 		$this->assertEquals('0', $this->config['test_lock'], 'First lock is released');
 
 		$lock2 = new phpbb_lock_db('test_lock', $this->config, $this->db);
 		$this->assertTrue($lock2->acquire());
+		$this->assertTrue($lock2->owns_lock());
 		$this->assertFalse(empty($this->config['test_lock']), 'Second lock is acquired');
 
 		$this->lock->release();
+		$this->assertTrue($lock2->owns_lock());
 		$this->assertFalse(empty($this->config['test_lock']), 'Double release of first lock is ignored');
 
 		$lock2->release();
diff --git a/tests/lock/flock_test.php b/tests/lock/flock_test.php
index 1edc96b3a4..8f0b866ab3 100644
--- a/tests/lock/flock_test.php
+++ b/tests/lock/flock_test.php
@@ -26,15 +26,21 @@ class phpbb_lock_flock_test extends phpbb_test_case
 		$lock = new phpbb_lock_flock($path);
 		$ok = $lock->acquire();
 		$this->assertTrue($ok);
+		$this->assertTrue($lock->owns_lock());
 		$lock->release();
+		$this->assertFalse($lock->owns_lock());
 
 		$ok = $lock->acquire();
 		$this->assertTrue($ok);
+		$this->assertTrue($lock->owns_lock());
 		$lock->release();
+		$this->assertFalse($lock->owns_lock());
 
 		$ok = $lock->acquire();
 		$this->assertTrue($ok);
+		$this->assertTrue($lock->owns_lock());
 		$lock->release();
+		$this->assertFalse($lock->owns_lock());
 	}
 
 	/* This hangs the process.
@@ -77,15 +83,18 @@ class phpbb_lock_flock_test extends phpbb_test_case
 			$ok = $lock->acquire();
 			$delta = time() - $start;
 			$this->assertTrue($ok);
+			$this->assertTrue($lock->owns_lock());
 			$this->assertGreaterThan(0.5, $delta, 'First lock acquired too soon');
 
 			$lock->release();
+			$this->assertFalse($lock->owns_lock());
 
 			// acquire again, this should be instantaneous
 			$start = time();
 			$ok = $lock->acquire();
 			$delta = time() - $start;
 			$this->assertTrue($ok);
+			$this->assertTrue($lock->owns_lock());
 			$this->assertLessThan(0.1, $delta, 'Second lock not acquired instantaneously');
 
 			// reap the child
@@ -99,8 +108,10 @@ class phpbb_lock_flock_test extends phpbb_test_case
 			$lock = new phpbb_lock_flock($path);
 			$ok = $lock->acquire();
 			$this->assertTrue($ok);
+			$this->assertTrue($lock->owns_lock());
 			sleep(2);
 			$lock->release();
+			$this->assertFalse($lock->owns_lock());
 
 			// and go away silently
 			pcntl_exec('/usr/bin/env', array('true'));
diff --git a/tests/tree/fixtures/phpbb_forums.xml b/tests/tree/fixtures/phpbb_forums.xml
new file mode 100644
index 0000000000..8f133078a9
--- /dev/null
+++ b/tests/tree/fixtures/phpbb_forums.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<dataset>
+	<table name="phpbb_forums">
+		<column>forum_id</column>
+		<column>parent_id</column>
+		<column>left_id</column>
+		<column>right_id</column>
+		<column>forum_parents</column>
+		<column>forum_name</column>
+		<column>forum_desc</column>
+		<column>forum_rules</column>
+	</table>
+</dataset>
diff --git a/tests/tree/nestedset_forum_base.php b/tests/tree/nestedset_forum_base.php
new file mode 100644
index 0000000000..776e822280
--- /dev/null
+++ b/tests/tree/nestedset_forum_base.php
@@ -0,0 +1,90 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+class phpbb_tests_tree_nestedset_forum_base extends phpbb_database_test_case
+{
+	public function getDataSet()
+	{
+		return $this->createXMLDataSet(dirname(__FILE__) . '/fixtures/phpbb_forums.xml');
+	}
+
+	protected $forum_data = array(
+		// \__/
+		1	=> array('forum_id' => 1, 'parent_id' => 0, 'user_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+		2	=> array('forum_id' => 2, 'parent_id' => 1, 'user_id' => 0, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+		3	=> array('forum_id' => 3, 'parent_id' => 1, 'user_id' => 0, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+		// \  /
+		//  \/
+		4	=> array('forum_id' => 4, 'parent_id' => 0, 'user_id' => 0, 'left_id' => 7, 'right_id' => 12, 'forum_parents' => 'a:0:{}'),
+		5	=> array('forum_id' => 5, 'parent_id' => 4, 'user_id' => 0, 'left_id' => 8, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+		6	=> array('forum_id' => 6, 'parent_id' => 5, 'user_id' => 0, 'left_id' => 9, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+
+		// \_  _/
+		//   \/
+		7	=> array('forum_id' => 7, 'parent_id' => 0, 'user_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+		8	=> array('forum_id' => 8, 'parent_id' => 7, 'user_id' => 0, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+		9	=> array('forum_id' => 9, 'parent_id' => 7, 'user_id' => 0, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+		10	=> array('forum_id' => 10, 'parent_id' => 9, 'user_id' => 0, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+		11	=> array('forum_id' => 11, 'parent_id' => 7, 'user_id' => 0, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => 'a:0:{}'),
+
+		// Non-existent forums
+		0	=> array('forum_id' => 0, 'parent_id' => 0, 'user_id' => 0, 'left_id' => 0, 'right_id' => 0, 'forum_parents' => 'a:0:{}'),
+		200	=> array('forum_id' => 200, 'parent_id' => 0, 'user_id' => 0, 'left_id' => 0, 'right_id' => 0, 'forum_parents' => 'a:0:{}'),
+	);
+
+	protected $set,
+		$config,
+		$lock,
+		$db;
+
+	public function setUp()
+	{
+		parent::setUp();
+
+		$this->db = $this->new_dbal();
+
+		global $config;
+
+		$config = $this->config = new phpbb_config(array('nestedset_forum_lock' => 0));
+		set_config(null, null, null, $this->config);
+
+		$this->lock = new phpbb_lock_db('nestedset_forum_lock', $this->config, $this->db);
+		$this->set = new phpbb_tree_nestedset_forum($this->db, $this->lock, 'phpbb_forums');
+
+		$this->set_up_forums();
+
+		$sql = "UPDATE phpbb_forums
+			SET forum_parents = 'a:0:{}'";
+		$this->db->sql_query($sql);
+	}
+
+	protected function set_up_forums()
+	{
+		$this->create_forum('Parent with two flat children');
+		$this->create_forum('Flat child #1', 1);
+		$this->create_forum('Flat child #2', 1);
+
+		$this->create_forum('Parent with two nested children');
+		$this->create_forum('Nested child #1', 4);
+		$this->create_forum('Nested child #2', 5);
+
+		$this->create_forum('Parent with flat and nested children');
+		$this->create_forum('Mixed child #1', 7);
+		$this->create_forum('Mixed child #2', 7);
+		$this->create_forum('Nested child #1 of Mixed child #2', 9);
+		$this->create_forum('Mixed child #3', 7);
+	}
+
+	protected function create_forum($name, $parent_id = 0)
+	{
+		$forum = $this->set->insert(array('forum_name' => $name, 'forum_desc' => '', 'forum_rules' => ''));
+		$this->set->change_parent($forum['forum_id'], $parent_id);
+	}
+}
diff --git a/tests/tree/nestedset_forum_get_data_test.php b/tests/tree/nestedset_forum_get_data_test.php
new file mode 100644
index 0000000000..ca1863e55e
--- /dev/null
+++ b/tests/tree/nestedset_forum_get_data_test.php
@@ -0,0 +1,119 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+require_once dirname(__FILE__) . '/nestedset_forum_base.php';
+
+class phpbb_tests_tree_nestedset_forum_get_data_test extends phpbb_tests_tree_nestedset_forum_base
+{
+	public function get_path_and_subtree_data_data()
+	{
+		return array(
+			array(1, true, true, array(1, 2, 3)),
+			array(1, true, false, array(2, 3)),
+			array(1, false, true, array(3, 2, 1)),
+			array(1, false, false, array(3, 2)),
+
+			array(2, true, true, array(1, 2)),
+			array(2, true, false, array(1)),
+			array(2, false, true, array(2, 1)),
+			array(2, false, false, array(1)),
+
+			array(5, true, true, array(4, 5, 6)),
+			array(5, true, false, array(4, 6)),
+			array(5, false, true, array(6, 5, 4)),
+			array(5, false, false, array(6, 4)),
+		);
+	}
+
+	/**
+	* @dataProvider get_path_and_subtree_data_data
+	*/
+	public function test_get_path_and_subtree_data($forum_id, $order_asc, $include_item, $expected)
+	{
+		$this->assertEquals($expected, array_keys($this->set->get_path_and_subtree_data($forum_id, $order_asc, $include_item)));
+	}
+
+	public function get_path_data_data()
+	{
+		return array(
+			array(1, true, true, array(1)),
+			array(1, true, false, array()),
+			array(1, false, true, array(1)),
+			array(1, false, false, array()),
+
+			array(2, true, true, array(1, 2)),
+			array(2, true, false, array(1)),
+			array(2, false, true, array(2, 1)),
+			array(2, false, false, array(1)),
+
+			array(5, true, true, array(4, 5)),
+			array(5, true, false, array(4)),
+			array(5, false, true, array(5, 4)),
+			array(5, false, false, array(4)),
+		);
+	}
+
+	/**
+	* @dataProvider get_path_data_data
+	*/
+	public function test_get_path_data($forum_id, $order_asc, $include_item, $expected)
+	{
+		$this->assertEquals($expected, array_keys($this->set->get_path_data($forum_id, $order_asc, $include_item)));
+	}
+
+	public function get_subtree_data_data()
+	{
+		return array(
+			array(1, true, true, array(1, 2, 3)),
+			array(1, true, false, array(2, 3)),
+			array(1, false, true, array(3, 2, 1)),
+			array(1, false, false, array(3, 2)),
+
+			array(2, true, true, array(2)),
+			array(2, true, false, array()),
+			array(2, false, true, array(2)),
+			array(2, false, false, array()),
+
+			array(5, true, true, array(5, 6)),
+			array(5, true, false, array(6)),
+			array(5, false, true, array(6, 5)),
+			array(5, false, false, array(6)),
+		);
+	}
+
+	/**
+	* @dataProvider get_subtree_data_data
+	*/
+	public function test_get_subtree_data($forum_id, $order_asc, $include_item, $expected)
+	{
+		$this->assertEquals($expected, array_keys($this->set->get_subtree_data($forum_id, $order_asc, $include_item)));
+	}
+
+	public function get_path_basic_data_data()
+	{
+		return array(
+			array(1, '', array()),
+			array(1, serialize(array()), array()),
+			array(2, '', array(1)),
+			array(2, serialize(array(1 => array())), array(1)),
+			array(10, '', array(7, 9)),
+			array(10, serialize(array(7 => array(), 9 => array())), array(7, 9)),
+		);
+	}
+
+	/**
+	* @dataProvider get_path_basic_data_data
+	*/
+	public function test_get_path_basic_data($forum_id, $forum_parents, $expected)
+	{
+		$forum_data = $this->forum_data[$forum_id];
+		$forum_data['forum_parents'] = $forum_parents;
+		$this->assertEquals($expected, array_keys($this->set->get_path_basic_data($forum_data)));
+	}
+}
diff --git a/tests/tree/nestedset_forum_insert_delete_test.php b/tests/tree/nestedset_forum_insert_delete_test.php
new file mode 100644
index 0000000000..d0e9e02c2e
--- /dev/null
+++ b/tests/tree/nestedset_forum_insert_delete_test.php
@@ -0,0 +1,120 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+require_once dirname(__FILE__) . '/nestedset_forum_base.php';
+
+class phpbb_tests_tree_nestedset_forum_add_remove_test extends phpbb_tests_tree_nestedset_forum_base
+{
+	public function delete_data()
+	{
+		return array(
+			array(1, array(1, 2, 3), array(
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 2, 'right_id' => 5),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 3, 'right_id' => 4),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 16),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 10, 'right_id' => 13),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 11, 'right_id' => 12),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+			)),
+			array(2, array(2), array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 4),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 5, 'right_id' => 10),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 6, 'right_id' => 9),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 7, 'right_id' => 8),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 20),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 13),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 17),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 15, 'right_id' => 16),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 18, 'right_id' => 19),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider delete_data
+	*/
+	public function test_delete($forum_id, $expected_deleted, $expected)
+	{
+		$this->assertEquals($expected_deleted, $this->set->delete($forum_id));
+
+		$result = $this->db->sql_query("SELECT forum_id, parent_id, left_id, right_id
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC");
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+
+	public function delete_throws_data()
+	{
+		return array(
+			array('Not an item', 0),
+			array('Item does not exist', 200),
+		);
+	}
+
+	/**
+	* @dataProvider delete_throws_data
+	*
+	* @expectedException			OutOfBoundsException
+	* @expectedExceptionMessage		FORUM_NESTEDSET_INVALID_ITEM
+	*/
+	public function test_delete_throws($explain, $forum_id)
+	{
+		$this->set->delete($forum_id);
+	}
+
+	public function insert_data()
+	{
+		return array(
+			array(array(
+				'forum_desc'	=> '',
+				'forum_rules'	=> '',
+				'forum_id'		=> 12,
+				'parent_id'		=> 0,
+				'left_id'		=> 23,
+				'right_id'		=> 24,
+				'forum_parents'	=> '',
+			), array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+
+				array('forum_id' => 12, 'parent_id' => 0, 'left_id' => 23, 'right_id' => 24),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider insert_data
+	*/
+	public function test_insert($expected_data, $expected)
+	{
+		$this->assertEquals($expected_data, $this->set->insert(array(
+			'forum_desc'	=> '',
+			'forum_rules'	=> '',
+		)));
+
+		$result = $this->db->sql_query('SELECT forum_id, parent_id, left_id, right_id
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC');
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+}
diff --git a/tests/tree/nestedset_forum_move_test.php b/tests/tree/nestedset_forum_move_test.php
new file mode 100644
index 0000000000..fe506c8278
--- /dev/null
+++ b/tests/tree/nestedset_forum_move_test.php
@@ -0,0 +1,569 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+require_once dirname(__FILE__) . '/nestedset_forum_base.php';
+
+class phpbb_tests_tree_nestedset_forum_move_test extends phpbb_tests_tree_nestedset_forum_base
+{
+	public function move_data()
+	{
+		return array(
+			array('Move first item up',
+				1, 1, false, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+			array('Move last item down',
+				7, -1, false, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+			array('Move first item down',
+				1, -1, true, array(
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 2, 'right_id' => 5),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 3, 'right_id' => 4),
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 10, 'right_id' => 11),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+			array('Move second item up',
+				4, 1, true, array(
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 2, 'right_id' => 5),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 3, 'right_id' => 4),
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 10, 'right_id' => 11),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+			array('Move last item up',
+				7, 1, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 16),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 10, 'right_id' => 13),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 11, 'right_id' => 12),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 17, 'right_id' => 22),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 18, 'right_id' => 21),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 19, 'right_id' => 20),
+			)),
+			array('Move last item up by 2',
+				7, 2, true, array(
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 10),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 4, 'right_id' => 7),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 5, 'right_id' => 6),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 16),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 12, 'right_id' => 13),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 17, 'right_id' => 22),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 18, 'right_id' => 21),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 19, 'right_id' => 20),
+			)),
+			array('Move last item up by 100',
+				7, 100, true, array(
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 10),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 4, 'right_id' => 7),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 5, 'right_id' => 6),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 16),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 12, 'right_id' => 13),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 17, 'right_id' => 22),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 18, 'right_id' => 21),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 19, 'right_id' => 20),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider move_data
+	*/
+	public function test_move($explain, $forum_id, $delta, $expected_moved, $expected)
+	{
+		$this->assertEquals($expected_moved, $this->set->move($forum_id, $delta));
+
+		$result = $this->db->sql_query("SELECT forum_id, parent_id, left_id, right_id
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC");
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+
+	public function move_down_data()
+	{
+		return array(
+			array('Move last item down',
+				7, false, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+			array('Move first item down',
+				1, true, array(
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 2, 'right_id' => 5),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 3, 'right_id' => 4),
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 10, 'right_id' => 11),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider move_down_data
+	*/
+	public function test_move_down($explain, $forum_id, $expected_moved, $expected)
+	{
+		$this->assertEquals($expected_moved, $this->set->move_down($forum_id));
+
+		$result = $this->db->sql_query("SELECT forum_id, parent_id, left_id, right_id
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC");
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+
+	public function move_up_data()
+	{
+		return array(
+			array('Move first item up',
+				1, false, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5),
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+			array('Move second item up',
+				4, true, array(
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 2, 'right_id' => 5),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 3, 'right_id' => 4),
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 8, 'right_id' => 9),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 10, 'right_id' => 11),
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider move_up_data
+	*/
+	public function test_move_up($explain, $forum_id, $expected_moved, $expected)
+	{
+		$this->assertEquals($expected_moved, $this->set->move_up($forum_id));
+
+		$result = $this->db->sql_query("SELECT forum_id, parent_id, left_id, right_id
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC");
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+
+	public function move_children_data()
+	{
+		return array(
+			array('Item has no children',
+				2, 1, false, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => 'a:0:{}'),
+			)),
+			array('Move to same parent',
+				4, 4, false, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => 'a:0:{}'),
+			)),
+			array('Move single child up',
+				5, 1, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 8, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 6, 'parent_id' => 1, 'left_id' => 6, 'right_id' => 7, 'forum_parents' => ''),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 9, 'right_id' => 12, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 10, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => 'a:0:{}'),
+			)),
+			array('Move nested children up',
+				4, 1, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 1, 'left_id' => 6, 'right_id' => 9, 'forum_parents' => ''),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 7, 'right_id' => 8, 'forum_parents' => ''),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 12, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => 'a:0:{}'),
+			)),
+			array('Move single child down',
+				5, 7, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 9, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 13, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 15, 'right_id' => 16, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 18, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 6, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => ''),
+
+			)),
+			array('Move nested children down',
+				4, 7, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 8, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 9, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 10, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 13, 'right_id' => 14, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 7, 'left_id' => 18, 'right_id' => 21, 'forum_parents' => ''),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 19, 'right_id' => 20, 'forum_parents' => ''),
+			)),
+			array('Move single child to parent 0',
+				5, 0, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 9, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 20, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 13, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 15, 'right_id' => 16, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 18, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 6, 'parent_id' => 0, 'left_id' => 21, 'right_id' => 22, 'forum_parents' => ''),
+			)),
+			array('Move nested children to parent 0',
+				4, 0, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 8, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 9, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 10, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 13, 'right_id' => 14, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 5, 'parent_id' => 0, 'left_id' => 19, 'right_id' => 22, 'forum_parents' => ''),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => ''),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider move_children_data
+	*/
+	public function test_move_children($explain, $forum_id, $target_id, $expected_moved, $expected)
+	{
+		$this->assertEquals($expected_moved, $this->set->move_children($forum_id, $target_id));
+
+		$result = $this->db->sql_query("SELECT forum_id, parent_id, left_id, right_id, forum_parents
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC");
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+
+	public function move_children_throws_item_data()
+	{
+		return array(
+			array('Item 0 does not exist', 0, 5),
+			array('Item does not exist', 200, 5),
+		);
+	}
+
+	/**
+	* @dataProvider move_children_throws_item_data
+	*
+	* @expectedException			OutOfBoundsException
+	* @expectedExceptionMessage		FORUM_NESTEDSET_INVALID_ITEM
+	*/
+	public function test_move_children_throws_item($explain, $forum_id, $target_id)
+	{
+		$this->set->move_children($forum_id, $target_id);
+	}
+
+	public function move_children_throws_parent_data()
+	{
+		return array(
+			array('New parent is child', 4, 5),
+			array('New parent is child 2', 7, 9),
+			array('New parent does not exist', 1, 200),
+		);
+	}
+
+	/**
+	* @dataProvider move_children_throws_parent_data
+	*
+	* @expectedException			OutOfBoundsException
+	* @expectedExceptionMessage		FORUM_NESTEDSET_INVALID_PARENT
+	*/
+	public function test_move_children_throws_parent($explain, $forum_id, $target_id)
+	{
+		$this->set->move_children($forum_id, $target_id);
+	}
+
+	public function change_parent_data()
+	{
+		return array(
+			array('Move single child up',
+				6, 1, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 8, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 6, 'parent_id' => 1, 'left_id' => 6, 'right_id' => 7, 'forum_parents' => ''),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 9, 'right_id' => 12, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 10, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => 'a:0:{}'),
+			)),
+			array('Move nested children up',
+				5, 1, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 1, 'left_id' => 6, 'right_id' => 9, 'forum_parents' => ''),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 7, 'right_id' => 8, 'forum_parents' => ''),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 12, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => 'a:0:{}'),
+			)),
+			array('Move single child down',
+				6, 7, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 9, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 13, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 15, 'right_id' => 16, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 18, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 6, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => ''),
+			)),
+			array('Move nested children down',
+				5, 7, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 8, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 9, 'right_id' => 22, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 10, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 13, 'right_id' => 14, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 7, 'left_id' => 18, 'right_id' => 21, 'forum_parents' => ''),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 19, 'right_id' => 20, 'forum_parents' => ''),
+			)),
+			array('Move single child to parent 0',
+				6, 0, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 10, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 9, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 11, 'right_id' => 20, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 13, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 15, 'right_id' => 16, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 18, 'right_id' => 19, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 6, 'parent_id' => 0, 'left_id' => 21, 'right_id' => 22, 'forum_parents' => ''),
+			)),
+			array('Move nested children to parent 0',
+				5, 0, true, array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 8, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 9, 'right_id' => 18, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 10, 'right_id' => 11, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 12, 'right_id' => 15, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 13, 'right_id' => 14, 'forum_parents' => 'a:0:{}'),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 17, 'forum_parents' => 'a:0:{}'),
+
+				array('forum_id' => 5, 'parent_id' => 0, 'left_id' => 19, 'right_id' => 22, 'forum_parents' => ''),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => ''),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider change_parent_data
+	*/
+	public function test_change_parent($explain, $forum_id, $target_id, $expected_moved, $expected)
+	{
+		$this->assertEquals($expected_moved, $this->set->change_parent($forum_id, $target_id));
+
+		$result = $this->db->sql_query("SELECT forum_id, parent_id, left_id, right_id, forum_parents
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC");
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+
+	public function change_parent_throws_item_data()
+	{
+		return array(
+			array('Item 0 does not exist', 0, 5),
+			array('Item does not exist', 200, 5),
+		);
+	}
+
+	/**
+	* @dataProvider change_parent_throws_item_data
+	*
+	* @expectedException			OutOfBoundsException
+	* @expectedExceptionMessage		FORUM_NESTEDSET_INVALID_ITEM
+	*/
+	public function test_change_parent_throws_item($explain, $forum_id, $target_id)
+	{
+		$this->set->change_parent($forum_id, $target_id);
+	}
+
+	public function change_parent_throws_parent_data()
+	{
+		return array(
+			array('New parent is child', 4, 5),
+			array('New parent is child 2', 7, 9),
+			array('New parent does not exist', 1, 200),
+		);
+	}
+
+	/**
+	* @dataProvider change_parent_throws_parent_data
+	*
+	* @expectedException			OutOfBoundsException
+	* @expectedExceptionMessage		FORUM_NESTEDSET_INVALID_PARENT
+	*/
+	public function test_change_parent_throws_parent($explain, $forum_id, $target_id)
+	{
+		$this->set->change_parent($forum_id, $target_id);
+	}
+}
diff --git a/tests/tree/nestedset_forum_regenerate_test.php b/tests/tree/nestedset_forum_regenerate_test.php
new file mode 100644
index 0000000000..38338dbc4d
--- /dev/null
+++ b/tests/tree/nestedset_forum_regenerate_test.php
@@ -0,0 +1,72 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+require_once dirname(__FILE__) . '/nestedset_forum_base.php';
+
+class phpbb_tests_tree_nestedset_forum_regenerate_test extends phpbb_tests_tree_nestedset_forum_base
+{
+	protected $fixed_set = array(
+		array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => ''),
+		array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3, 'forum_parents' => ''),
+		array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5, 'forum_parents' => ''),
+
+		array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12, 'forum_parents' => ''),
+		array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11, 'forum_parents' => ''),
+		array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10, 'forum_parents' => ''),
+
+		array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22, 'forum_parents' => ''),
+		array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15, 'forum_parents' => ''),
+		array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19, 'forum_parents' => ''),
+		array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18, 'forum_parents' => ''),
+		array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => ''),
+	);
+
+	public function regenerate_left_right_ids_data()
+	{
+		return array(
+			array('UPDATE phpbb_forums
+				SET left_id = 0,
+					right_id = 0', false),
+			array('UPDATE phpbb_forums
+				SET left_id = 28,
+					right_id = 28
+				WHERE left_id > 12', false),
+			array('UPDATE phpbb_forums
+				SET left_id = left_id * 2,
+					right_id = right_id * 2', false),
+			array('UPDATE phpbb_forums
+				SET left_id = left_id * 2,
+					right_id = right_id * 2
+				WHERE left_id > 12', false),
+			array('UPDATE phpbb_forums
+				SET left_id = left_id - 4,
+					right_id = right_id * 4
+				WHERE left_id > 4', false),
+			array('UPDATE phpbb_forums
+				SET left_id = 0,
+					right_id = 0
+				WHERE left_id > 12', true),
+		);
+	}
+
+	/**
+	* @dataProvider regenerate_left_right_ids_data
+	*/
+	public function test_regenerate_left_right_ids($breaking_query, $reset_ids)
+	{
+		$result = $this->db->sql_query($breaking_query);
+
+		$this->assertEquals(23, $this->set->regenerate_left_right_ids(1, 0, $reset_ids));
+
+		$result = $this->db->sql_query('SELECT forum_id, parent_id, left_id, right_id, forum_parents
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC');
+		$this->assertEquals($this->fixed_set, $this->db->sql_fetchrowset($result));
+	}
+}
diff --git a/tests/tree/nestedset_forum_test.php b/tests/tree/nestedset_forum_test.php
new file mode 100644
index 0000000000..516c794ffc
--- /dev/null
+++ b/tests/tree/nestedset_forum_test.php
@@ -0,0 +1,116 @@
+<?php
+/**
+*
+* @package tree
+* @copyright (c) 2013 phpBB Group
+* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
+*
+*/
+
+require_once dirname(__FILE__) . '/nestedset_forum_base.php';
+
+class pphpbb_tests_tree_nestedset_forum_test extends phpbb_tests_tree_nestedset_forum_base
+{
+	public function forum_constructor_data()
+	{
+		return array(
+			array(array(
+				array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6),
+				array('forum_id' => 2, 'parent_id' => 1, 'left_id' => 2, 'right_id' => 3),
+				array('forum_id' => 3, 'parent_id' => 1, 'left_id' => 4, 'right_id' => 5),
+
+				array('forum_id' => 4, 'parent_id' => 0, 'left_id' => 7, 'right_id' => 12),
+				array('forum_id' => 5, 'parent_id' => 4, 'left_id' => 8, 'right_id' => 11),
+				array('forum_id' => 6, 'parent_id' => 5, 'left_id' => 9, 'right_id' => 10),
+
+				array('forum_id' => 7, 'parent_id' => 0, 'left_id' => 13, 'right_id' => 22),
+				array('forum_id' => 8, 'parent_id' => 7, 'left_id' => 14, 'right_id' => 15),
+				array('forum_id' => 9, 'parent_id' => 7, 'left_id' => 16, 'right_id' => 19),
+				array('forum_id' => 10, 'parent_id' => 9, 'left_id' => 17, 'right_id' => 18),
+				array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider forum_constructor_data
+	*/
+	public function test_forum_constructor($expected)
+	{
+		$result = $this->db->sql_query('SELECT forum_id, parent_id, left_id, right_id
+			FROM phpbb_forums
+			ORDER BY left_id, forum_id ASC');
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+
+	public function get_sql_where_data()
+	{
+		return array(
+			array('SELECT forum_id
+				FROM phpbb_forums
+				%s
+				ORDER BY forum_id ASC',
+				'WHERE', '', array(
+				array('forum_id' => 1),
+				array('forum_id' => 2),
+				array('forum_id' => 3),
+
+				array('forum_id' => 4),
+				array('forum_id' => 5),
+				array('forum_id' => 6),
+
+				array('forum_id' => 7),
+				array('forum_id' => 8),
+				array('forum_id' => 9),
+				array('forum_id' => 10),
+				array('forum_id' => 11),
+			)),
+			array('SELECT f.forum_id
+				FROM phpbb_forums f
+				%s
+				ORDER BY f.forum_id ASC',
+				'WHERE', 'f.', array(
+				array('forum_id' => 1),
+				array('forum_id' => 2),
+				array('forum_id' => 3),
+
+				array('forum_id' => 4),
+				array('forum_id' => 5),
+				array('forum_id' => 6),
+
+				array('forum_id' => 7),
+				array('forum_id' => 8),
+				array('forum_id' => 9),
+				array('forum_id' => 10),
+				array('forum_id' => 11),
+			)),
+			array('SELECT forum_id
+				FROM phpbb_forums
+				WHERE forum_id < 4 %s
+				ORDER BY forum_id ASC',
+				'AND', '', array(
+				array('forum_id' => 1),
+				array('forum_id' => 2),
+				array('forum_id' => 3),
+			)),
+			array('SELECT f.forum_id
+				FROM phpbb_forums f
+				WHERE f.forum_id < 4 %s
+				ORDER BY f.forum_id ASC',
+				'AND', 'f.', array(
+				array('forum_id' => 1),
+				array('forum_id' => 2),
+				array('forum_id' => 3),
+			)),
+		);
+	}
+
+	/**
+	* @dataProvider get_sql_where_data
+	*/
+	public function test_get_sql_where($sql_query, $operator, $column_prefix, $expected)
+	{
+		$result = $this->db->sql_query(sprintf($sql_query, $this->set->get_sql_where($operator, $column_prefix)));
+		$this->assertEquals($expected, $this->db->sql_fetchrowset($result));
+	}
+}