The day-to-day use of django-nose is mostly transparent; just run
test as usual.
./manage.py help test for all the options nose provides, and look to
the nose docs for more help with nose.
Enabling Database Reuse¶
You can save several seconds at the beginning and end of your test suite by
reusing the test database from the last run. To do this, set the environment
REUSE_DB to 1:
REUSE_DB=1 ./manage.py test
The one new wrinkle is that, whenever your DB schema changes, you should leave the flag off the next time you run tests. This will cue the test runner to reinitialize the test database.
Also, REUSE_DB is not compatible with TransactionTestCases that leave junk in the DB, so be sure to make your TransactionTestCases hygienic (see below) if you want to use it.
Enabling Fast Fixtures¶
There are several known issues with this feature.
django-nose includes a fixture bundler which drastically speeds up your tests by eliminating redundant setup of Django test fixtures. To use it...
django.test.TestCase. (I like to import it
as TestCasein my project’s
tests/__init__.pyand then import it from there into my actual tests. Then it’s easy to sub the base class in and out.) This alone will cause fixtures to load once per class rather than once per test.
- Activate fixture bundling by passing the
./manage.py test. This loads each unique set of fixtures only once, even across class, module, and app boundaries.
How Fixture Bundling Works¶
The fixture bundler reorders your test classes so that ones with identical sets of fixtures run adjacently. It then advises the first of each series to load the fixtures once for all of them (and the remaining ones not to bother). It also advises the last to tear them down. Depending on the size and repetition of your fixtures, you can expect a 25% to 50% speed increase.
Incidentally, the author prefers to avoid Django fixtures, as they encourage irrelevant coupling between tests and make tests harder to comprehend and modify. For future tests, it is better to use the “model maker” pattern, creating DB objects programmatically. This way, tests avoid setup they don’t need, and there is a clearer tie between a test and the exact state it requires. The fixture bundler is intended to make existing tests, which have already committed to fixtures, more tolerable.
--with-fixture-bundling causes test failures, it likely indicates
an order dependency between some of your tests. Here are the most frequent
sources of state leakage we have encountered:
- Locale activation, which is maintained in a threadlocal variable. Be sure to reset your locale selection between tests.
- memcached contents. Be sure to flush between tests. Many test superclasses do this automatically.
It’s also possible that you have
post_save signal handlers which create
additional database rows while loading the fixtures.
isn’t yet smart enough to notice this and clean up after it, so you’ll have to
go back to plain old
TestCase for now.
Exempting A Class From Bundling¶
In some unusual cases, it is desirable to exempt a test class from fixture
bundling, forcing it to set up and tear down its fixtures at the class
boundaries. For example, we might have a
TestCase subclass which sets up
some state outside the DB in
setUpClass and tears it down in
tearDownClass, and it might not be possible to adapt those routines to heed
the advice of the fixture bundler. In such a case, simply set the
exempt_from_fixture_bundling attribute of the test class to
Speedy Hygienic TransactionTestCases¶
Unlike the stock Django test runner, django-nose lets you write custom TransactionTestCase subclasses which expect to start with an unmarred DB, saving an entire DB flush per test.
The default Django TransactionTestCase class can leave the DB in an unclean state when it’s done. To compensate, TransactionTestCase does a time-consuming flush of the DB before each test to ensure it begins with a clean slate. Django’s stock test runner then runs TransactionTestCases last so they don’t wreck the environment for better-behaved tests. django-nose replicates this behavior.
Escaping the Grime¶
Some people, however, have made subclasses of TransactionTestCase that clean up after themselves (and can do so efficiently, since they know what they’ve changed). Like TestCase, these may assume they start with a clean DB. However, any TransactionTestCases that run before them and leave a mess could cause them to fail spuriously.
django-nose offers to fix this. If you include a special attribute on your well-behaved TransactionTestCase...
class MyNiceTestCase(TransactionTestCase): cleans_up_after_itself = True
...django-nose will run it before any of those nasty, trash-spewing test cases. You can thus enjoy a big speed boost any time you make a TransactionTestCase clean up after itself: skipping a whole DB flush before every test. With a large schema, this can save minutes of IO.
django-nose’s own FastFixtureTestCase uses this feature, even though it ultimately acts more like a TestCase than a TransactionTestCase.
If you have a model that is used only by tests (for example, to test an
abstract model base class), you can put it in any file that’s imported in the
course of loading tests. For example, if the tests that need it are in
test_models.py, you can put the model in there, too. django-nose will make
sure its DB table gets created.
django-nose.tools provides pep8 versions of Django’s TestCase asserts
and some of its own as functions.
assert_redirects(response, expected_url, status_code=302, target_status_code=200, host=None, msg_prefix='') assert_contains(response, text, count=None, status_code=200, msg_prefix='') assert_not_contains(response, text, count=None, status_code=200, msg_prefix='') assert_form_error(response, form, field, errors, msg_prefix='') assert_template_used(response, template_name, msg_prefix='') assert_template_not_used(response, template_name, msg_prefix='') assert_queryset_equal(qs, values, transform=repr) assert_num_queries(num, func=None, *args, **kwargs) assert_code(response, status_code, msg_prefix='') assert_ok(response, msg_prefix='') assert_mail_count(count, msg=None)
Always Passing The Same Options¶
To always set the same command line options you can use a nose.cfg or setup.cfg (as usual) or you can specify them in settings.py like this:
NOSE_ARGS = ['--failed', '--stop']
If you need to make custom plugins, you can define each plugin class somewhere within your app and load them from settings.py like this:
NOSE_PLUGINS = [ 'yourapp.tests.plugins.SystematicDysfunctioner', # ... ]
Just like middleware or anything else, each string must be a dot-separated, importable path to an actual class. Each plugin class will be instantiated and added to the Nose test runner.