Mon, 01 Oct 2007
Use your Nose!
Every programmer out there [hopefully] knows that unittests are an essential part of any growing body of code, especially in the open source world. However, most hackers out either never write test cases (let alone comments), or usually put them off until "later" (aka: never). Having to deal with Java and JUnit tests in college not only made me not want to write unit tests, but it made me want to kill myself and everyone around me. Thankfully, I learned Python.
So, I just happen to maintain a piece of software in Fedora called nose (which lives in the python-nose package). Nose is a discovery-based unittest extension for Python, and is also a part of the TurboGears stack. If you're hacking on a TurboGears project, the turbogears.testutil module provides some incredibly useful features that make writing tests powerfully trivial.
For example, in the code below (taken from bodhi), I create a test case that utilizes a fresh SQLite database in memory. Inheriting from the the testutil.DBTest parent class, this database will be created and torn down automagically before and after each test case is run -- ensuring that my tests are executed in complete isolation. With this example, I wrote a test case to ensure that unauthenticated people cannot create a new update.
import urllib, cherrypy
from turbogears import update_config, database, testutil, url
update_config(configfile='dev.cfg', modulename='bodhi.config')
database.set_db_uri("sqlite:///:memory:")
class TestControllers(testutil.DBTest):
def test_unauthenticated_update(self):
params = {
'builds' : 'TurboGears-1.0.2.2-2.fc7',
'release' : 'Fedora 7',
'type' : 'enhancement',
'bugs' : '1234 5678',
'cves' : 'CVE-2020-0001',
'notes' : 'foobar'
}
path = url('/save?' + urllib.urlencode(params))
testutil.createRequest(path, method='POST')
assert "You must provide your credentials before accessing this resource." in cherrypy.response.body[0]
In the above example, the TestControllers class is automatically detected by nose, which then executes each method that begins with the word 'test'. To run your unittests, just type 'nosetests'.
[lmacken@tomservo bodhi]$ nosetests
.................................
----------------------------------------------------------------------
Ran 33 tests in 16.798s
OK
profile:
nosetests --with-profile --profile-stats-file=nose.prof
python -c "import hotshot.stats ; stats = hotshot.stats.load('nose.prof') ; stats.sort_stats('time', 'calls') ; stats.print_stats(20)"
[lmacken@tomservo bodhi]$ make profile
nosetests --with-profile --profile-stats-file=nose.prof
.................................
----------------------------------------------------------------------
Ran 33 tests in 42.878s
OK
python -c "import hotshot.stats ; stats = hotshot.stats.load('nose.prof') ; stats.sort_stats('time', 'calls') ; stats.print_stats(20)"
800986 function calls (702850 primitive calls) in 42.878 CPU seconds
Ordered by: internal time, call count
List reduced from 3815 to 20 due to restriction <20>
ncalls tottime percall cumtime percall filename:lineno(function)
14 13.675 0.977 13.675 0.977 /usr/lib/python2.5/socket.py:71(ssl)
31 10.683 0.345 10.683 0.345 /usr/lib/python2.5/httplib.py:994(_read)
2478/2429 9.297 0.004 9.677 0.004 :1()
1 0.604 0.604 0.604 0.604 /usr/lib/python2.5/commands.py:50(getstatusoutput)
2999 0.536 0.000 0.539 0.000 /usr/lib/python2.5/site-packages/sqlobject/sqlite/sqliteconnection.py:177(_executeRetry)
105899 0.448 0.000 0.773 0.000 Modules/pyexpat.c:871(Default)
60 0.327 0.005 1.102 0.018 /usr/lib/python2.5/site-packages/kid/parser.py:343(_buildForeign)
105899 0.325 0.000 0.325 0.000 /usr/lib/python2.5/site-packages/kid/parser.py:452(_default)
3396 0.280 0.000 0.420 0.000 /usr/lib/python2.5/site-packages/cherrypy/config.py:107(get)
2965 0.263 0.000 0.263 0.000 /usr/lib/python2.5/logging/__init__.py:364(formatTime)
44964/6587 0.238 0.000 0.252 0.000 /usr/lib/python2.5/site-packages/kid/parser.py:156(_pull)
60 0.116 0.002 0.116 0.002 /usr/lib/python2.5/site-packages/kid/compiler.py:38(py_compile)
8127 0.114 0.000 0.114 0.000 /usr/lib/python2.5/site-packages/cherrypy/_cputil.py:311(lower_to_camel)
8982 0.110 0.000 0.137 0.000 /usr/lib/python2.5/site-packages/sqlobject/dbconnection.py:902(__getattr__)
13740/4044 0.108 0.000 2.176 0.001 /usr/lib/python2.5/site-packages/kid/parser.py:209(_coalesce)
24353/4026 0.107 0.000 2.143 0.001 /usr/lib/python2.5/site-packages/kid/parser.py:174(_track)
3170 0.093 0.000 0.398 0.000 /usr/lib/python2.5/logging/__init__.py:405(format)
1 0.082 0.082 0.082 0.082 /usr/lib/python2.5/site-packages/rpm/__init__.py:5()
4777 0.081 0.000 1.320 0.000 /usr/lib/python2.5/site-packages/kid/serialization.py:564(generate)
759/176 0.074 0.000 0.210 0.001 /usr/lib/python2.5/sre_parse.py:385(_parse)
posted at: 09:40 | link | | 3 comments
Posted by gioby at Thu Feb 5 03:48:31 2009
Thank you for the example and for the makefile tip, I was looking for something like this.
Cheers!
Posted by Christopher Perkins at Mon Jan 18 18:13:38 2010
Luke,
keep in mind, you will only get benefits to use as many processes you have cores because of the GIL. In fact, it's best to limit it to the number of cores so you don't have to worry about GIL contention.
cheers.
-chris
Posted by Jason R. Coombs at Tue Jan 19 07:54:33 2010
Too cool. Thanks for pointing that out!
Chris, if nose is using the multiprocess module, and if I understand correctly, each process is forked into its own Python interpreter, each with its own GIL, and then processes are synchronized with serialized objects. So in that case, GIL contention wouldn't come into the picture.
