[Vm-dev] VM stability / unit tests

[Phil B]

While I've been enjoying the fantastic performance improvements we've seen
from Cog onward, one thing I've been less excited about are some of the
stability/functionality issues I've been running into.  They are not
numerous (maybe 1/2 dozen or so major ones in the last 5 years) but they
are getting quite tedious to isolate and replicate.  Recent examples that
come to mind include the 64-bit primHighResClock truncation and 'could not
grow remembered set' issues  (My current joy is a case where I have an
#ifTrue: block that doesn't get executed unless I convert it to an
#ifTrue:ifFalse: with a noop for the ifFalse:.. I'll provide a reproducible
test case as soon as I'm able.  The specific issue isn't the issue, but
rather that I keep hitting things like this that seem rather fundamental
yet edge-casey at the same time)

I don't expect perfection as a phenomenal amount of progress is being made
by a small group of people but I am beginning to wonder if the existing
unit tests are sufficient to adequately exercise the VM? I.e. so that the
VM developers are aware that a recent change may have broken something or
are the existing tests mainly oriented towards image and bytecode VM
development?  Just some food for thought and wanted to see if it's just me
having these sorts of issues...

Thanks,
Phil
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