Django Testing

Django Testing
Eric Holscher
http://ericholscher.com

Tuesday, May 5, 2009 1

How do you know?

• First 4 months of my job was porting and testing
Ellington

• Going from Django r1290 to Django 1.0.
• Suite from 0 to 400 tests.


30,000 Ft View

• State of testing in Django
• Why you should be testing
• How you start testing
• Useful tools
• Eventual Goals


State of Django Testing


assertTrue('Hello World', community.testing.status)


Django 1.1

Making Testing Possible since 2009


manage.py startapp
creates a tests.py


from django.test import TestCase

class SimpleTest(TestCase):
def test_basic_addition(self):
quot;quot;quot;
Tests that 1 + 1 always equals 2.
quot;quot;quot;
self.failUnlessEqual(1 + 1, 2)

__test__ = {quot;doctestquot;: quot;quot;quot;
Another way to test that 1 + 1 is equal to 2.

>>> 1 + 1 == 2
True
quot;quot;quot;}


Fast Tests
(Transactions)


Minutes (Lower is better)

Ellington Test Speedup
60

45

30

15

0
Django 1.0 Django 1.1


You now have no excuse.


Why to test


Scary

Less Scary

Not Scary

Peace of Mind

Code must adapt


“It is not the strongest of
the species that survives, nor
the most intelligent, but the
one most responsive to
change.”
- Charles Darwin


Won’t somebody please
think of the users?!


Tests as Documentation


Tests as Documentation

Test driven development
+
Document driven development
=
Test Driven Documentation


“Code without tests is
broken as designed”
- Jacob Kaplan-Moss


Dizzying Array of Testing
Options


What kind of test?

• doctest
• unittest


Doctests

• Inline documentation
• <Copy from terminal to test ﬁle>
• Can’t use PDB
• Hide real failures
• “Easy”


def parse_ttag(token, required_tags):
quot;quot;quot;
A function to parse a template tag.

It sets the name of the tag to 'tag_name' in the hash returned.

>>> from test_utils.templatetags.utils import parse_ttag
>>> parse_ttag('super_cool_tag for my_object as obj', ['as'])
{'tag_name': u'super_cool_tag', u'as': u'obj'}
>>> parse_ttag('super_cool_tag for my_object as obj', ['as', 'for'])
{'tag_name': u'super_cool_tag', u'as': u'obj', u'for': u'my_object'}

quot;quot;quot;
bits = token.split(' ')
tags = {'tag_name': bits.pop(0)}
for index, bit in enumerate(bits):
bit = bit.strip()
if bit in required_tags:
if len(bits) != index-1:
tags[bit] = bits[index+1]
return tags


Unit Tests

• Use for everything else
• More rubust
• setUp and tearDown
• Standard (XUnit)


import random
import unittest

class TestRandom(unittest.TestCase):

def setUp(self):
self.seq = range(10)

def testshuffle(self):
# make sure the shuffled sequence does not lose any elements
random.shuffle(self.seq)
self.seq.sort()
self.assertEqual(self.seq, range(10))

if __name__ == '__main__':
unittest.main()


Django TestCase

• Subclasses unittest
• Fixtures
• Assertions
• Mail
• URLs


Test Client

• Test HTTP Requests without server
• Test Views, Templates, and Context


from django.contrib.auth.models import User
from django.test import TestCase
from django.core import mail

class PasswordResetTest(TestCase):
fixtures = ['authtestdata.json']
urls = 'django.contrib.auth.urls'

def test_email_not_found(self):
quot;Error is raised if the provided email address isn't currently registeredquot;
response = self.client.get('/password_reset/')
self.assertEquals(response.status_code, 200)
response = self.client.post('/password_reset/', {'email': 'not_a_real_email@email.com'})
self.assertContains(response, quot;That e-mail address doesn't have an associated user
accountquot;)
self.assertEquals(len(mail.outbox), 0)


What ﬂavor of test?

• Unit
• Functional
• Browser


Unit test

• Low level tests
• Small, focused, exercising one bit of functionality


Regression test

• Written when you ﬁnd a bug
• Proves bug was ﬁxed
• Django Tickets


Functional

• “Black Box Testing”
• Check High Level Functionality


Functional Testing Tools

• Twill
• Django Test Client
• ...


Ellington

• Lots of different clients
• Need to test deployment (Functional)


go {{ site.url }}/marketplace/search/
formvalue 1 q pizza
submit
code 200


Pretty Functional Tests

Can test

• All sites on a server
• All sites of a certain type
• A single problemed client
• A test across all sites


Browser tests

• Run tests in a web browser
• Check compatibility of design
• Basically an IE sanity check
• Only real way to test JS, AJAX, CSS


Browser Testing Tools

• Windmill
• Selenium


Other kinds of testing

• Spiders
• Fuzz testing
• Load testing
• Prayer


Where do I start?


Fixed a bug


Poking at code on the
command line


Pony turned Horse


Now what?


Start with a regression
test or a functional test


Use unittest unless you
have a reason not to!


Use the data, Luke

• Use data as a pivot
• Fixtures means you use Unit Tests
• Creation on the command line, Doctests


Creating Fixtures

• ./manage.py dumpdata <app>
• ./manage.py makeﬁxture Model[x:y]
• Follows relations
• By Hand


TestShell

./manage.py testshell <ﬁxture>


Making Functional tests

• Usually a relatively annoying process
• Testmaker makes it easy.
• ./manage.py testmaker <app>
• Simply browse and your session is recorded.


Testing your views
generally gets you the
most coverage.


80% Case


When > Where


Tools


Coverage


Mock Objects

• http://www.voidspace.org.uk/python/mock/


import unittest
from mock import Mock

from templatetags.cms_tags import if_link_is_active, IsActiveNode

class TestIsActiveTag(unittest.TestCase):
def test_returns_correct_node_type(self):
token = Mock(methods=['split_contents'])
token.split_contents.return_value = ('if_link_is_active',
'bar')

self.assertEqual(type(if_link_is_active(Mock(), token)),
IsActiveNode)


Custom Test Runners


Django Test Extensions

• Gareth Rushgrove
• Extra Assertions
• Coverage and XML Test Runners
• http://github.com/garethr/django-test-extensions


Django Sane Testing

• Ella Folk, Lucas (Hi!)
• Based on nosetests
• Selenium
• Live server
• http://devel.almad.net/trac/django-sane-testing/


Django Test Utils

• Mine!
• Testmaker
• Crawler
• Random fanciness
• http://github.com/ericholscher/django-test-utils/tree/
master


Recording tests is
generally seen as bad.


My philosophy

• Write tests.
• Notice patterns and best practices
• Automate recording of tests with those patterns
• If you can’t automate, use tools to make it easier.


Process for testmaker

• Most view tests check status_code and response
context

• Write middleware that catches this info
• Records it to a ﬁle
• Err on the side of more data.


Goals
(That perfect world)


Some form of TDD

• Write tests as you write code
• Makes your code easy to test


Follow Django’s Model

• Tests with every commit
• Docs with every commit
• Run tests before commiting


Use a DVCS

• At work we have a central SVN repo
• Git feature branches
• Code is staged for documentation and testing
• Committed to SVN once it is “done”


Continuous Integration


NEVER LEAVE THE
BUILD BROKEN


Love Green

Fast(er) Tests


JSON


Proﬁling

python -m cProﬁle manage.py test


Mock Objects

http://www.voidspace.org.uk/python/mock/


Future and Ponies


Summer of Code

• Test-Only Models
• Coverage
• Windmill tests of the admin


Test Suites in Django


Central Testing
Repository


Nose Plugin Integration


Things to remember

• Testing is not hard, you just have to get started.
• If your code doesn’t have tests, it will be hard/
impossible to refactor

• Once you have tests, you need to run them!


Credits

• http://www.flickr.com/photos/tym/192416981/
• http://www.flickr.com/photos/seandreilinger/2459266781/
• http://www.homebabysafety.com/images/baby_crawl_suit.jpg
• http://www.flickr.com/photos/pinkypigs/960572985/


Django Testing

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