[openstack-dev] Proposal for including fake implementations in python-client packages
joe.gordon0 at gmail.com
Thu Jul 4 09:12:13 UTC 2013
On Wed, Jul 3, 2013 at 6:19 PM, Christopher Armstrong <
chris.armstrong at rackspace.com> wrote:
> On Tue, Jul 2, 2013 at 11:38 PM, Robert Collins
> <robertc at robertcollins.net> wrote:
> > Radix points out I missed the naunce that you're targeting the users
> > of python-novaclient, for instance, rather than python-novaclient's
> > own tests.
> > On 3 July 2013 16:29, Robert Collins <robertc at robertcollins.net> wrote:
> >>> What I'd like is for each client library, in addition to the actual
> >>> implementation, is that they ship a fake, in-memory, version of the
> API. The
> >>> fake implementations should take the same arguments, have the same
> >>> values, raise the same exceptions, and otherwise be identical, besides
> >>> fact
> >>> that they are entirely in memory and never make network requests.
> >> So, +1 on shipping a fake reference copy of the API.
> >> -1 on shipping it in the client.
> >> The server that defines the API should have two implementations - the
> >> production one, and a testing fake. The server tests should exercise
> >> *both* code paths [e.g. using testscenarios] to ensure there is no
> >> skew between them.
> >> Then the client tests can be fast and efficient but not subject to
> >> implementation skew between fake and prod implementations.
> >> Back on Launchpad I designed a similar thing, but with language
> >> neutrality as a goal :
> >> And in fact, I think that that design would work well here, because we
> >> have multiple language bindings - Python, Ruby, PHP, Java, Go etc, and
> >> all of them will benefit from a low(ms or less)-latency test fake.
> > So taking the aspect I missed into account I'm much happier with the
> > idea of shipping a fake in the client, but... AFAICT many of our
> > client behaviours are only well defined in the presence of a server
> > anyhow.
> > So it seems to me that a fast server fake can be used in tests of
> > python-novaclient, *and* in tests of code using python-novaclient
> > (including for instance, heat itself), and we get to write it just
> > once per server, rather than once per server per language binding.
> > -Rob
> I want to make sure I understond you. Let's say I have a program named
> cool-cloud-tool, and it uses python-novaclient, python-keystoneclient,
> and three other clients for OpenStack services. You're suggesting that
> its test suite should start up instances of all those OpenStack
> services with in-memory or otherwise localized backends, and
> communicate with them using standard python-*client functionality?
> I can imagine that being a useful thing, if it's very easy to do, and
> won't increase my test execution time too much.
The easiest way to do this would be to set up a devstack instance to run
your tests against, but that would increase test execution time by at least
a few minutes. So although something like this would not work well for
unit tests it could be useful for integration tests.
Also I do not know of anyone using this for this type of testing yet, but
someone always has to be first.
> IRC: radix
> Christopher Armstrong
> OpenStack-dev mailing list
> OpenStack-dev at lists.openstack.org
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