You don't want to get me started on test patterns. Emerging specs require PRBS31, which is a stupid choice because it's so long that no equipment (not even BERTs) can measure TJ with appreciable statistical significance on that pattern.
Check the DesignCon site for a paper last year by Marty Miller on test pattern lengths.
I wrote one for Tek, but the link seems to have gone away. Send me a note and I'll get it to you: email@example.com