Yes, and the title() method also works as expected in this context, which is why your output includes "title:Title Test".

Your error is coming from the following line, where it calls track()->toCString() because, as others have stated, track() returns a plain integer, not an object, and plain integers don't have object methods. Because they're not objects.

Change that line to say 'track', $file->tag()->track(); and it will do what you presumably want it to. (Namely, it will print "track0".)