Checkout his blog entry The modern programming professional has GUTs.
He (Alistair) suggests that there is a shift in assertion by Bob on what makes a true professional. Though Bob starts with TDD, he seems to agree that to be a professional you need to have good unit tests.Alistair believes that, till date, there has been no good term for "good unit tests," as there is for TDD. Had there been a term like 'GUTs' for good unit tests then people could brag about GUTs without implying whether they were written before or after the code.
I could not resist the title :-)