Resources for AtomPub parser validation

[Daniel Jalkut <jalkut@xxxxxxxxxxxxxxx>]

There are well-known and trusted public feed validators for Atom and  
RSS. What I'm curious to know is whether anybody has resources to  
share for testing/validating the parsers of such feeds.

In  particular, I continue to have mind-bending problems interpreting  
the ins and outs of how particular content needs to be treated in the  
Atom format that is used by AtomPub.  Right now, for instance, I'm  
trying to learn definitively whether an escaped "&" inside a  
content type xhtml div should be left alone or converted to an  
ampersand in the parsed content output.

It would be a great aid if there was some "reference" feed that  
exercised many of the common mistakes parsers make, and at the same  
time expressed definitive advice for how these entities should be  
handled.

Anybody know of such a resource?

Daniel