PHP Unit testing and mocking a file system scandir() - unit-testing

Question

I have a method in a class that scans a directory and creates an array of all the subdirectories. It's pretty simple and works great. However, I would like to add a unit test for this method and I am having a hard time figuring out how.
Here's my problem: I can create a virtual file system using vfsstream and it works fine. However, I can't pass that to my class to create an array from. It needs a real directory to scan. I want to test against a controlled directory (obviously so I know exactly what will the be result of every scan so I can test it). The scanned directory in production may change frequently.
So, my only solution is to create a test-specific fake directory in my test folders, pass that path to my scanner, and then check it against what I know to be in that fake directory. Is this best practice or am I missing something?
Thank you!
Here is some code:
The Test
function testPopulateAuto()
{
$c = new \Director\Core\Components\Components;
// The structure of the file system I am checking against. This is what I want to generate.
$check = array(
'TestFolder1',
'TestFolder2',
);
$path = dirname( __FILE__ ) . "/test-file-system/"; // Contains TestFolder1 and TestFolder1
$list = $c->generateList( $path ); // Scans the path and returns an array that should be identical to $check
$this->assertEquals($check, $list);
}

Answer 1

Sorry if I misunderstood your question, but scandir should work with custom stream. Example:
$structure = array(
'tmp' => array(
'music' => array(
'wawfiles' => array(
'mp3' => array(),
'hello world.waw' => 'nice song',
'abc.waw' => 'bad song',
'put that cookie down.waw' => 'best song ever',
"zed's dead baby.waw" => 'another cool song'
)
)
)
);
$vfs = vfsStream::setup('root');
vfsStream::create($structure, $vfs);
$music = vfsStream::url('root/tmp/music/wawfiles');
var_dump(scandir($music));
Output:
array(5) {
[0]=>
string(7) "abc.waw"
[1]=>
string(15) "hello world.waw"
[2]=>
string(3) "mp3"
[3]=>
string(24) "put that cookie down.waw"
[4]=>
string(19) "zed's dead baby.waw"
}