[openstack-dev] [infra]Requesting consideration of httmock package for test-requirements in Juno
Paul Michali (pcm)
pcm at cisco.com
Fri Apr 11 13:29:40 UTC 2014
See inline @PCM…
On Apr 9, 2014, at 5:56 PM, Jamie Lennox <jamielennox at redhat.com<mailto:jamielennox at redhat.com>> wrote:
----- Original Message -----
From: "Paul Michali (pcm)" <pcm at cisco.com<mailto:pcm at cisco.com>>
To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Sent: Wednesday, April 9, 2014 6:31:09 AM
Subject: Re: [openstack-dev] [infra]Requesting consideration of httmock package for test-requirements in Juno
On Apr 8, 2014, at 3:04 PM, Jamie Lennox < jamielennox at redhat.com<mailto:jamielennox at redhat.com> > wrote:
----- Original Message -----
From: "Paul Michali (pcm)" < pcm at cisco.com<mailto:pcm at cisco.com> >
To: "OpenStack Development Mailing List (not for usage questions)" <
openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org> >
Cc: jamielennox at gmail.com<mailto:jamielennox at gmail.com>
Sent: Wednesday, April 9, 2014 12:09:58 AM
Subject: [openstack-dev] [infra]Requesting consideration of httmock package
for test-requirements in Juno
Reposting this, after discussing with Sean Dague…
For background, I have developed a REST client lib to talk to a H/W device
with REST server for VPNaaS in Neutron. To support unit testing of this, I
created a UT module and a mock REST server module and used the httmock
package. I found it easy to use, and was able to easily create a sub-class
of my UT to run the same test cases with real H/W, instead of the mock REST
server. See the original email below, for links of the UT and REST mock to
see how I used it.
I created a bug under requirements, to propose adding httmock to the
test-requirements. Sean mentioned that there is an existing mock package,
called httpretty , which I found is used in keystone client UTs), and should
petition to see if httmock should replace httpretty, since the two appear to
overlap in functionality.
I found this link, with a brief comparison of the two:
http://marekbrzoska.wordpress.com/2013/08/28/mocking-http-requests-in-python/
So… I’m wondering if the community is interested in adopting this package
(with the goal of deprecating the httpretty package). Otherwise, I will work
on reworking the UT code I have to try to use httpretty.
Would be interested in peoples’ thoughts, especially those who have worked
with httpretty.
Thanks in advance!
So I introduced HTTPretty into the requirements and did the work around
keystoneclient and am well aware that it has a few warts.
PCM: Great, I grabbed your name from keystone client logs and was hoping you
had some knowledge of httpretty.
At the time we were going through the changeover from httplib to requests and
httpretty gave a good way to change over the library and ensure that we
hadn't actually changed the issued requests at all. If we had already been
on requests i don't know if i'd have made the same choice.
In general I am in favour of mocking the response layer rather than the
client layer - whether we do this with httpretty or httmock doesn't bother
me that much. Honestly I don't think a global patch of the requests Session
object is that much safer that a global patch of the socket interface, if
anything requests is under development and so this interface is less
defined.
PCM: Not sure that httmock can be considered a global patch. It is a context
lib that intercepts the call through various decorators where the request
can be filtered/processed and if not, will fall through and call the actual
library.
So, with the context lib, you can define several handlers for the request(s).
When the call is made, it will try each handler and if they all return None,
will call the original function, otherwise they return the value of the mock
routine. Here’s an example front he test cases I cerated:
with httmock.HTTMock(csr_request.token, csr_request.put,
csr_request.normal_get):
keepalive_info = {'interval': 60, 'retry': 4}
self.csr.configure_ike_keepalive (keepalive_info)
self.assertEqual(requests.codes.NO_CONTENT, self.csr.status)
content = self.csr.get_request ('vpn-svc/ike/keepalive')
self.assertEqual(requests.codes.OK, self.csr.status)
expected = {'periodic': False}
expected.update(keepalive_info)
self.assertDictContainsSubset(expected, content)
The client code (red) does a POST with authentication info to get token, does
a PUT with the setting, and then a GET to verify the value. The mock module
has these methods created:
@httmock.urlmatch ( netloc =r'localhost')
def token( url , request):
if ' auth /token-services' in url.path:
return {'status_code': requests.codes.OK,
'content': {'token-id': 'dummy-token'}}
@httmock.urlmatch ( netloc =r'localhost')
def normal_get( url , request):
if request.method != 'GET':
return
if not request.headers.get('X- auth -token', None):
return {'status_code': requests.codes.UNAUTHORIZED}
…
if 'vpn-svc/ike/keepalive' in url.path:
content = {u'interval': 60,
u'retry': 4,
u'periodic': True}
return httmock.response(requests.codes.OK, content=content)
@httmock.urlmatch(netloc=r'localhost')
def put(url, request):
if request.method != 'PUT':
return
if not request.headers.get('X-auth-token', None):
return {'status_code': requests.codes.UNAUTHORIZED}
return {'status_code': requests.codes.NO_CONTENT}
Just a few notes….
A) Could have created separate context lib for put vs get.
B) Could have a method for specific URI request matches (I do that in some
places, in others I catch all requests).
C) Can filter the requests based on request type or URI.
D) Can catch all URLs or filter.
E) Additional decorators can be created for these handlers.
F) There is lots of flexibility with manipulating the response data.
For (C) I’ve done things like this:
@filter_request(['post'], 'vpn-svc/site-to-site')
@httmock.urlmatch(netloc=r'localhost')
def post_missing_ipsec_policy(url, request):
if not request.headers.get('X-auth-token', None):
return {'status_code': requests.codes.UNAUTHORIZED}
return {'status_code': requests.codes.BAD_REQUEST}
For (D), I have all my handlers set for localhost, and then I have another
test module that creates a subclass of the test class, sets the host to an
IP of a live system, and runs the same tests, only this time against a live
router, instead the mock module. This saves a lot of coding and allows me to
reuse the test code (and make sure it REALLY works with real hardware, in my
case).
For (E), I did this to simulate a timeout in a request and then latter
success on retry:
@filter_request (['get'], 'global/host-name')
@repeat(1)
@httmock.urlmatch ( netloc =r'localhost')
def expired_request( url , request):
"""Simulate access denied failure on first request for this resource.
Intent here is to simulate that the token has expired, by failing
the first request to the resource. Because of the repeat=1, this
will only be called once, and subsequent calls will not be handled
by this function, but instead will access the normal handler and
will pass. Currently configured for a GET request, but will work
with POST and PUT as well. For DELETE, would need to filter_request on a
different resource (e.g. 'global/local-users')
"""
return {'status_code': requests.codes.UNAUTHORIZED}
Ref:
https://github.com/openstack/neutron/blob/master/neutron/tests/unit/services/vpn/device_drivers/notest_cisco_csr_rest.py
Ref:
https://github.com/openstack/neutron/blob/master/neutron/tests/unit/services/vpn/device_drivers/cisco_csr_mock.py
The reason that i call this a global mock is that behind the context manager it is still patching the class method not an individual instance of a requests.Session object. see: https://github.com/patrys/httmock/blob/master/httmock.py#L142
@PCM Good point. I forgot that it did that.
Everything you have specified is doable with httpretty.
@httpretty.activate does the mocking of the library (socket rather than requests.Session) then you use
httpretty.register_uri(httpretty.GET,
'http://testurl/testpath',
body=json.dumps({'hello': 'world'},
status=200)
You can do the same multiple queued responses, responses via callbck and everything else. Also the thing i find a use a lot that i don't see provided by httmock is things like:
self.assertEqual(httpretty.last_request().headers['X-Auth-Token'],
expected_token)
In which you test that the request that you send is actually what you expect as well.
@PCM So this is testing that what was sent to the code under test is what it sends out in the HTTP request? I’m not sure I see the advantage in testing that. I usually just test that the response is correct, given the request data I send to the code under test.
Anyway there is a pretty long readme on the github page: https://github.com/gabrielfalcao/HTTPretty that explains these sort of features.
@PCM Thanks. I’ll take a look at this.
What i would like to see though is this mocking transferred into fixtures
like in https://review.openstack.org/#/c/77961/ and have the actual choice
in mock library hidden behind those fixtures. Is this a pattern that httmock
can handle? or something else again?
PCM I see your point - it would be nice to be able to have the flexibility to
swap the underlying mock libraries. Would have to think about it more, to
see if a common fixture can be used for httpretty and httmock. I’m not sure
if they are different enough (one monkey patching, one using context lib)
that it would be possible (and I don’t have a strong understanding of
httpretty yet).
Would love to hear peoples’ thoughts no this.
Again, i'm not that strongly in favour of HTTPretty over httmock (though missing last_request will be a problem).
@PCM I’ll take a look and see if I can change all my UTs to use HTTPretty. I’ll be curious to see if it can handle all the cases I use. In particular, I have two test modules, one which has test cases that, by using a URL directed to the localhost, makes use of a mock REST server, to exercise my client REST module.
I have a second test module, which has subclasses for the test classes in the first module, only in setup, it specifies the URL of a “real” REST server. When I run this module, which is very small, it leverages off all the test cases, but verifies with a real device, which is the true proof that the REST client under test actually works. Granted, it wouldn’t be used during a UT TOX run, but it could be used with a Tempest run.
>From an httmock standpoint there is no change, as the handler methods have filters to only catch requests to a URL directed to localhost. The “live” test will end up falling through and making a REST request to a real server.
Likewise, I have tests for checking timeouts, where I have the desired call map to the mock, so the request fails, but other requests flow through to the live server.
Any thoughts on how I would be able to do these things with HTTPretty?
My point is just that the two libraries can both do the same job and i'm wondering what the advantage of the new one is.
@PCM One thing is that I think the context manager technique of handling the mocking is (subjectively) a really clean way to do things. The other is this duality of calls passing through to a real (non-mock) server without altering the test cases.
As mentioned i would really like to see this moved into fixtures - httpretty will allow that somewhat, i don't see that httmock will,
@PCM My guess is that probably either method could be wrapped by a fixture, but I’m also guessing that they are different enough such that it may be very hard to come up with a fixture to accommodate both.
and if i had the time i think i would just rewrite a library like this making use of the tools we already have like mock, fixtures, and testresources. (My other thought is to just subclass a requests.Session object with an overridden request method -rather than a global patch- and allow that to be passed into clients but i don't think they all support that).
@PCM I’ll try to see if I can adapt my UTs to use HTTPretty and think a little bit on how a test fixture could be used.
Regards,
PCM (Paul Michali)
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Jamie
PCM (Paul Michali)
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Jamie
PCM (Paul Michali)
MAIL …..…. pcm at cisco.com<mailto:pcm at cisco.com>
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On Apr 4, 2014, at 10:44 AM, Paul Michali (pcm) < pcm at cisco.com<mailto:pcm at cisco.com> > wrote:
I’d like to get this added to the test-requirements for Neutron. It is a very
flexible HTTP mock module that works with the Requests package. It is a
decorator that wraps the Request’s send() method and allows easy mocking of
responses, etc (w/o using a web server).
The bug is: https://bugs.launchpad.net/neutron/+bug/1282855
Initially I had requested both httmock and newer requests, but was requested
to separate them, so this is to target httmock as it is more important (to
me :) to get approval,
The review request is: https://review.openstack.org/#/c/75296/
An example of code that would use this:
https://github.com/openstack/neutron/blob/master/neutron/tests/unit/services/vpn/device_drivers/notest_cisco_csr_rest.py
https://github.com/openstack/neutron/blob/master/neutron/tests/unit/services/vpn/device_drivers/cisco_csr_mock.py
Looking forward to hearing whether or not we can include this package into
Juno.
Thanks in advance!
PCM (Paul Michali)
MAIL …..…. pcm at cisco.com
IRC ……..… pcm_ ( irc.freenode.com )
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