I think something is not functioning in my brain (hopefuly it's the just the hunger :hamburger: ), but I'm not totally grok'ing this test.  Where does the `reassign` come into play?  Group and owner are `sids[:guest]` and then two extra ACEs are added to the DACL for `sids[:guest]`.  

So it's written and then read back... and we find that we have at least 2 ACEs for `sids[:guest]`.  But I'm not clear on what that verifies.

Do you mean that it `merges` ACEs for the same SID (in which case we'd verify that less than 4 were written)?  When I saw `reassign` I was expecting to see the call to the new `reassign(old_sid, new_sid)` method on `AccessControlList` that switches the ACEs from one SID to another.