public function is_dir()
{
$this->assertTrue(is_dir($this->fooURL));
$this->assertTrue(is_dir($this->fooURL . '/.'));
$this->assertTrue(is_dir($this->barURL));
$this->assertTrue(is_dir($this->barURL . '/.'));
$this->assertFalse(is_dir($this->baz1URL));
$this->assertFalse(is_dir($this->baz2URL));
$this->assertFalse(is_dir($this->fooURL . '/another'));
$this->assertFalse(is_dir(vfsStream::url('another')));
}