public function setUp()
{
$this->rootDirectory = vfsStream::newDirectory('/');
$this->rootDirectory->addChild(vfsStream::newDirectory('var/log/app'));
$dir = $this->rootDirectory->getChild('var/log/app');
$dir->addChild(vfsStream::newDirectory('app1'));
$dir->addChild(vfsStream::newDirectory('app2'));
$dir->addChild(vfsStream::newDirectory('foo'));
}