Python/tox, start a process before tests, shut it down when done

Question

I'm using Tox to check that the system I'm developing is behaving well when installed in a fresh environment (+ sanity checking the setup.py file). However, the system uses a memcached server, and ideally I'd like to spawn a new one for every Tox run.

Is there a preferred way to start programs before tests are run (and shut them down afterwards) or will I need to write a custom runner?

Edit: The test runner is py.test

You should probably do this in the _setup_ functions/methods of the actual unit testing framework (_py.test_, _nose_, _unittests_, ...) you are using with _tox_. — Pedro Romano, Nov 13 '12 at 10:43
Good idea! Implementation was a breeze with `subprocess`. Make it an answer and I'll accept it. — Jacob Oscarson, Nov 13 '12 at 13:32
Implementation note: `pytest_configure` and `pytest_unconfigure` in `conftest.py` was a good place to spawn/terminate. — Jacob Oscarson, Nov 13 '12 at 13:36

score 11 · Answer 1 · answered Nov 14 '12 at 08:35

To elaborate on flub's comment on the best way to do it with py.test, using its fixture mechanism. Create a conftest.py file with this content:

# content of conftest.py

import pytest, subprocess

@pytest.fixture(scope="session", autouse=True)
def startmemcache(request):
    proc = subprocess.Popen(...)
    request.addfinalizer(proc.kill)

The "autouse" flag means that this fixture will be activated for each test run without requiring any references from tests. In practise, however, you might want to make the connection details to the subprocess available to your tests so that you don't have to work with magic port numbers. You wouldn't use "autouse" then but rather return a fixture object for connecting to memcache, nicely encapsulating test configuration in one place (the fixture function). See the docs for many more examples.

Much nicer than my initial implementation. I'll go for that. — Jacob Oscarson, Nov 14 '12 at 09:24

score 2 · Accepted Answer · answered Nov 13 '12 at 13:37

2

This isn't really a task for tox. My recommendation is that you do this in the setup functions/methods of the actual unit testing framework (py.test, nose, unittests, ...) you are using with tox.

Original poster's comment:

pytest_configure and pytest_unconfigure in conftest.py was a good place to spawn/terminate.

answered Nov 13 '12 at 13:37

Pedro Romano

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pytest_configure/unconfigure are not the best for this since they will not work well with distributed testing (pytest-xdist plugin). The py.test 2.3 release introduced the enhanced fixtures API to solve this problem, mark the fixture with @pytest.fixture(scope='session') to create a session-scoped fixture. – flub Nov 13 '12 at 15:47

score 1 · Answer 3 · answered Nov 13 '12 at 10:47

1

I recommend that you use paver - http://paver.github.com/paver/ - for the spawning up and shutting down of your memcached server or any additional "miscellaneous system admin tasks" that you need to do during the execution of setup.py by tox.

answered Nov 13 '12 at 10:47

Calvin Cheng

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but then you can't run the tests without tox anymore easily. Doing it with the underlying test runner fits better i think. – hpk42 Nov 14 '12 at 08:27

Python/tox, start a process before tests, shut it down when done

3 Answers3