On 01/07/2016 03:01 PM, Jim Rollenhagen wrote:
On Thu, Jan 07, 2016 at 02:41:12PM -0500, Sean Dague wrote:
On 01/07/2016 02:09 PM, Jim Rollenhagen wrote:
Hi all,
A change to global-requirements[1] introduces mimic, which is an http
server that can mock various APIs, including nova and ironic, including
control of error codes and timeouts. The ironic team plans to use this
for testing python-ironicclient without standing up a full ironic
environment.
Here's the catch - mimic is built on twisted. I know twisted was
previously removed from OpenStack (or at least people said "pls no", I
don't know the full history). We didn't intend to stealth-introduce
twisted back into g-r, but it was pointed out to me that it may appear
this way, so here I am letting everyone know. lifeless pointed out that
when tests are failing, people may end up digging into mimic or twisted
code, which most people in this community aren't familiar with AFAIK,
which is a valid point though I hope it isn't required often.
So, the primary question here is: do folks have a problem with adding
twisted here? We're holding off on Ironic changes that depend on this
until this discussion has happened, but aren't reverting the g-r change
until we decide one way or another.
// jim
[1] https://review.openstack.org/#/c/220268/
What is the advantage of running another server like this over using
requests-mock (which is used by other OpenStack projects for testing
today)? The only difference here seems to be that you actually execute
requests code in one case and not in the other.
Requests-mock debugging when things go wrong seems a bit simpler.
This is less about twisted and more about trying to not introduce yet
another way to mock code in the tree that people need to understand.
-Sean
We'd be using this for functional tests, not unit, where we can't really
inject mocks. The idea is that we could run a full functional suite
against either mimic or a full ironic environment, just by changing a
test setting.
I don't really see the point of a separate project like Mimic that has a
whole bunch of reimplementations (mocked out) of all sorts of OpenStack
(and RAX-specific) API services. It's just a great way to introduce a
larger surface area for bugs to creep in -- since you have to keep the
Mimic interfaces up to date with the real interfaces. Better to keep
something like this -- if it is TRULY needed -- in-tree with the API
service itself, so that the chances of divergence are reduced. This is
similar to the fakevirt driver in Nova. It's in tree for good reason:
when someone changes the virt driver interface, the fakevirt driver goes
boom and needs to be changed in a corresponding fashion in the same patch.
What value does a functional test against an HTTP API service that does
nothing (other than introduce greater surface area for bugs) actually
offer over unit tests anyway?
-jay
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