A Django project I’m working on defines two databases in its config: The standard/default internal db as well as a remote legacy read-only database belonging to my organization. Models for the read-only db were generated by
inspectdb, and naturally have
managed = False in their Meta class, which prevents Django from attempting any form of migration on them.
Unfortunately, that also prevents the Django test runner from trying to create a schema mirror of it during test runs. But what if you want to stub out some sample data from the read-only database into a fixture that can be loaded and accessed during unit tests? You’ll need to do the following:
- Tell Django to create the second test database locally rather than on the remote host
- Disable any routers you have that route queries for certain models through the remote db
- Tell Django to override the
Managed = False attribute in the Meta class during the test run
Putting that all together turned out to be a bit tricky, but it’s not bad once you understand how and why you need to take these steps. Because you’ll need to override a few settings during test runs only, it makes sense to create a separate
test_settings.py to keep everything together:
from project.local_settings import *
from django.test.runner import DiscoverRunner
Test runner that automatically makes all unmanaged models in your Django
project managed for the duration of the test run.
Many thanks to the Caktus Group: http://bit.ly/1N8TcHW
def setup_test_environment(self, *args, **kwargs):
from django.db.models.loading import get_models
self.unmanaged_models = [m for m in get_models() if not m._meta.managed]
for m in self.unmanaged_models:
m._meta.managed = True
super(UnManagedModelTestRunner, self).setup_test_environment(*args, **kwargs)
def teardown_test_environment(self, *args, **kwargs):
super(UnManagedModelTestRunner, self).teardown_test_environment(*args, **kwargs)
# reset unmanaged models
for m in self.unmanaged_models:
m._meta.managed = False
# Since we can't create a test db on the read-only host, and we
# want our test dbs created with postgres rather than the default, override
# some of the global db settings, only to be in effect when "test" is present
# in the command line arguments:
if 'test' in sys.argv or 'test_coverage' in sys.argv: # Covers regular testing and django-coverage
DATABASES['default']['ENGINE'] = 'django.db.backends.postgresql_psycopg2'
DATABASES['default']['HOST'] = '127.0.0.1'
DATABASES['default']['USER'] = 'username'
DATABASES['default']['PASSWORD'] = 'secret'
DATABASES['tmi']['ENGINE'] = 'django.db.backends.postgresql_psycopg2'
DATABASES['tmi']['HOST'] = '127.0.0.1'
DATABASES['tmi']['USER'] = 'username'
DATABASES['tmi']['PASSWORD'] = 'secret'
# The custom routers we're using to route certain ORM queries
# to the remote host conflict with our overridden db settings.
# Set DATABASE_ROUTERS to an empty list to return to the defaults
# during the test run.
DATABASE_ROUTERS = 
# Set Django's test runner to the custom class defined above
TEST_RUNNER = 'project.test_settings.UnManagedModelTestRunner'
With that in place, you can now run your tests with:
./manage.py test --settings=project.test_settings
… leaving settings untouched during normal site operations. You can now serialize some data from your read-only host and load it as a fixture in your tests:
# Load test data into both dbs:
fixtures = ['auth_group.json', 'sample_people.json']
# Guarantees that our sample data is being loaded in the test suite
person = Foo.objects.get(id=7000533)