File is supposed to be a stdClass file object and not a path to the file system. When using the file object is you would need a resolvable URI to load from as well.

Sample code you could use but leads to breaking other things:
`$file = new stdClass();
    $file->fid = NULL;
    $file->uri = drupal_get_path('module', 'islandora_pdf') . '/tests/fixtures/test.zip';
    $file->filename = 'test';
    $file->filemime = file_get_mimetype($file->uri);`