Some minutes ago I released vfsStream 0.4.0, introducing support for file modes, owners and groups. While I planned to implement this at least since a year it took me three tries to get it implemented, and while implementing this I stumbled about some issues which can not be solved by vfsStream. Major problem is that the PHP functions chmod(), chown() and chgrp() do not work with vfsStream URLs due to limitations imposed by PHP (or possibly by underlying C, not sure). The stream wrapper API has no support to enable setting file modes, owner or group of a userland stream implementation. This means the usage of file mode support is limited and can not be applied to create tests for classes using one of the three functions. However, it is still possible to use file modes for testing correct usage of is_readable(), is_writable() and is_executable(). Another usage scenario is to make sure directories created with mkdir() receive the correct file mode, see the file mode example. I'm sure users will come up with other usage scenarios I did not even thought of.
Beside this new feature the release contains a bugfix for vfsStreamDirectory::addChild() to make sure adding another child of the same name as an existing child replaces this existing child, and a fix to return correct results for stat() calls. Grab the release via it's pear channel pear.php-tools.net and try it out. I suspect the file mode support may contain bugs because I did not have the time to use it in other projects, but after all, it is still in alpha stage.