### Question:
TreeModelSupport { public void firePathChanged(TreePath path) { Object node = path.getLastPathComponent(); TreePath parentPath = path.getParentPath(); if (parentPath == null) fireChildrenChanged(path, null, null); else { Object parent = parentPath.getLastPathComponent(); fireChildChanged(parentPath, treeModel .getIndexOfChild(parent, node), node); } } TreeModelSupport(TreeModel model); void fireNewRoot(); void firePathLeafStateChanged(TreePath path); void fireTreeStructureChanged(TreePath subTreePath); void firePathChanged(TreePath path); void fireChildChanged(TreePath parentPath, int index, Object child); void fireChildrenChanged(TreePath parentPath, int[] indices,
            Object[] children); void fireChildAdded(TreePath parentPath, int index, Object child); void fireChildRemoved(TreePath parentPath, int index, Object child); void fireChildrenAdded(TreePath parentPath, int[] indices,
            Object[] children); void fireChildrenRemoved(TreePath parentPath, int[] indices,
            Object[] children); void addTreeModelListener(TreeModelListener l); TreeModelListener[] getTreeModelListeners(); void removeTreeModelListener(TreeModelListener l);  }### Answer:
@Test( expected = IllegalArgumentException.class ) public void testPathChangedNotNullPathElements() { final TreePath path = new TreePath( new Object[]{ null } ); support.firePathChanged( path ); }
@Test( expected = NullPointerException.class ) public void testPathChangedNotNullPath() { support.firePathChanged( null ); }