[libvirt] Scope of the test driver? (Was: Re: [PATCH] test_driver: implement virDomainSendKey)

[Peter Krempa]

On Mon, Jun 03, 2019 at 08:52:55 +0200, Erik Skultety wrote:
> On Mon, Jun 03, 2019 at 08:40:13AM +0200, Pavel Hrdina wrote:
> > On Mon, Jun 03, 2019 at 08:23:57AM +0200, Erik Skultety wrote:
> > > On Sat, Jun 01, 2019 at 02:46:56PM +0200, Ilias Stamatis wrote:

[...]

> > > I think this API should be merely about translating the value, because
> > > this way you're just blocking a synchronous API for no apparent benefit. I
> > > believe it should return instantaneously. On the other hand, I'm just wondering
> > > what value it brings having an API translating keycodes, but I guess for
> > > consistency reasons, we can happily introduce it.
> >
> > The benefit is to simulate the holdtime as for example hyperv driver is
> > doing, in QEMU we just pass everything to the QEMU itself where that one
> > will probably do similar operation.
> 
> Both hyperv and vbox have to do it because they don't support it, so they do
> usleep before sending down and up keycodes respectively, QEMU does it
> iternally. In test driver, you're not testing any true codes, so doing plain
> usleep si IMHO wrong, from app dev's perspective you're only testing whether
> usleep works by providing arbitrary time to wait, which raises the obvious
> question "why".

I think the problem here is that it's unclear what the purpose of the
test driver is supposed to be. Clarifying the purpose first might have
positive impact on the design decisions here.

So what's the point of the test driver?

Is it meant for human interaction, e.g. for application developers or
users wanting to test stuff? In that case you probably want to simulate
the "worst" behaviour we have, which would be the blocking timeout so
that users/devs can see the worst case implications of running such a
command.

Alternatively the purpose may be to allow some kind of "unit" testing
for APPs using libvirt. (I specifically used "unit" testing, because any
kind of sane real integration testing will not use the test driver
because it would not accomplish much). In such case the timeout is a
hassle because it just unnecessarily prolongs test runs and does not add
much value.

Any other ideas? I don't have any more.

Frankly even the two use cases above aren't something I'd recommend to
the users. In case of user/dev testing, checking against a real VM makes
more sense and the same goes for real integration testing. 
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