For a spec to become a REC today, it requires two 100% complete and fully interoperable implementations, which is proven by each successfully passing literally thousands of test cases (20,000 tests for the whole spec would probably be a conservative estimate)
The candidate recommendation phase, which WHATWG expects to happen next year is a much more relevant date. That aside I do wonder if this level of effort isn't just wasted pedantry.
From here http://wiki.whatwg.org/wiki/FAQ:
For a spec to become a REC today, it requires two 100% complete and fully interoperable implementations, which is proven by each successfully passing literally thousands of test cases (20,000 tests for the whole spec would probably be a conservative estimate)
The candidate recommendation phase, which WHATWG expects to happen next year is a much more relevant date. That aside I do wonder if this level of effort isn't just wasted pedantry.