I am excited to announce that I have completed my next grant milestone! I recently increased test coverage of extend_vtable.c to over 95% ( 95.5% to be exact), achieving the milestone with a half percent buffer. It definitely wasn't easy, but I changed the way I was approaching writing tests and it resulted in a huge burst of productivity.
I went through a test coverage report and wrote down, on an actual piece of paper, every function that had no test coverage. This allowed me to circle the functions that I thought would be easiest to write tests for, and quickly got those out of the way. I then went for uncovered functions that were similar to already covered functions, and then finally I got to the hard functions.
This was a fruitful exercise, because it was decided by Parrot developers that some VTABLE functions escaped accidentally and that they should be removed from the public API. Whiteknight++ removed Parrot_PMC_destroy (extra points for humor), which I was using incorrectly in the extend_vtable tests and which was actually coredumping Parrot, but only on certain platforms. I then removed Parrot_PMC_mark and Parrot_PMC_invoke, the first being an implementation detail of the garbage collector, and Parrot_PMC_invoke because it was the only function that returned a '''Parrot_Opcode_t*''' and basically not fit for public consumption.
I also created a ticket (TT#2126) for a bug in the Parrot_PMC_morph function, which has some possibly buggy but definitely unspecified behavior.
The remaining, untested functions in extend_vtable are clone_pmc, cmp_pmc, get_pointer_keyed_int, get_pointer_keyed_str, remove_vtable_override, set_pointer_keyed and set_pointer_keyed_str. I leave the testing of these functions as an exercise to the interested reader :)
This reminds me of a saying, I can't remember it exactly, but it is something about the best laid plans of camels and butterflies often taste like onions. Anyway, since I wrote my grant, the Parrot Embed API was deprecated and replaced with a shinier and better documented system. After talking with cotto++ and whiteknight++ on IRC, it was decided that working on test coverage for the new embed API was a better use of resources than writing tests for the old embed API that my original grant referred to, which will most likely be removed from Parrot soon.
To summarize, I have two grant milestones left, increasing extend.c (currently at 61% ) and embed/api.c to 95% coverage.
Given the lessons learned from testing extend_vtable and based on the fact that I have already made some headway, my new estimate for these milestones is three weeks each. To make this more definite, I plan to be done with this grant work by July 15th.
This is the home stretch! I can feel it in my bones.