I am still on the path of increasing test coverage in src/extend_vtable.c. It is much like a zen study, where you methodically concentrate on many tiny little pebbles, one at a time, moving them in the sand, to just the right place. According to the latest code coverage statistics, we are now at 72% code coverage, which is an increase of about 8% since my last report.
Many, many more tests involving Key PMCs were added. For an intro to what they are, take a look at my previous grant update. Many of the tests are clusters of related tests, because most VTABLEs have many similar forms which take integer, string or PMC-flavored keys. I ran into some platform-specific bugs which only manifest on Darwin machines, which were reported by Jim Keenan in TT# 2098 and which I then fixed by querying with a non-empty Key, which is more prudent.
I also ran into some actual bugs which I reported as Trac Tickets. First is that the cmp_pmc VTABLE does not seem to be working correctly from extend_vtable, which was reported in TT #2103. Then I fell into a "hole" in the VTABLE API, where ResizablePMCArray does not respond to defined_keyed(), which it should. This is described in TT #2094.
In retrospect, this was one of the most productive periods of my grant work. I estimate that I will be very close to the 95% milestone by my next grant update at this pace, which is very exciting.