Question

I have some unit tests I’ve written to test my Django application. One test suite in particular has a lot of code in its setUp() function. The purpose of said code is to create test data for the database. (Yes I know about fixtures and have chosen not to use them in this case). When I run the unit test suite the first test that is run passes, but then the rest of the tests in the suite fail. The message for all the failures is the same: it mentions that the error’s location is “self.database_object.save()” and that the cause is “IntegrityError: column name is not unique”. So, my best guess is that Django is not tearing down the database properly after each test.

Earlier today it was working, but I guess some refactoring I did messed it up. Any ideas on why Django is not properly tearing down the database after each test?

Answer 1

Do you use TestCase or TransactionTestCase for your base class? Sometimes this behavior is related to the optimization Django makes for TestCase in favor of TransactionTestCase. Here is the difference:

https://docs.djangoproject.com/en/dev/topics/testing/?from=olddocs#django.test.TransactionTestCase

class TransactionTestCase

Django TestCase classes make use of database
transaction facilities, if available, to speed up the process of
resetting the database to a known state at the beginning of each test.
A consequence of this, however, is that the effects of transaction
commit and rollback cannot be tested by a Django TestCase class. If
your test requires testing of such transactional behavior, you should
use a Django TransactionTestCase.

TransactionTestCase and TestCase are identical except for the manner
in which the database is reset to a known state and the ability for
test code to test the effects of commit and rollback. A
TransactionTestCase resets the database before the test runs by
truncating all tables and reloading initial data. A
TransactionTestCase may call commit and rollback and observe the
effects of these calls on the database.

A TestCase, on the other hand, does not truncate tables and reload
initial data at the beginning of a test. Instead, it encloses the test
code in a database transaction that is rolled back at the end of the
test. It also prevents the code under test from issuing any commit or
rollback operations on the database, to ensure that the rollback at
the end of the test restores the database to its initial state. In
order to guarantee that all TestCase code starts with a clean
database, the Django test runner runs all TestCase tests first, before
any other tests (e.g. doctests) that may alter the database without
restoring it to its original state.