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TransactionManagementError “You can't execute queries until the end of the 'atomic' block” while using signals, but only during Unit Testing

由 北战南征 提交于 2019-11-27 17:08:39
Cerin

I ran into this same problem myself. This is caused by a quirk in how transactions are handled in the newer versions of Django coupled with a unittest that intentionally triggers an exception.

I had a unittest that checked to make sure a unique column constraint was enforced by purposefully triggering an IntegrityError exception:

def test_constraint(self):
    try:
        # Duplicates should be prevented.
        models.Question.objects.create(domain=self.domain, slug='barks')
        self.fail('Duplicate question allowed.')
    except IntegrityError:
        pass

    do_more_model_stuff()

In Django 1.4, this works fine. However, in Django 1.5/1.6, each test is wrapped in a transaction, so if an exception occurs, it breaks the transaction until you explicitly roll it back. Therefore, any further ORM operations in that transaction, such as my do_more_model_stuff(), will fail with that django.db.transaction.TransactionManagementError exception.

Like caio mentioned in the comments, the solution is to capture your exception with transaction.atomic like:

from django.db import transaction
def test_constraint(self):
    try:
        # Duplicates should be prevented.
        with transaction.atomic():
            models.Question.objects.create(domain=self.domain, slug='barks')
        self.fail('Duplicate question allowed.')
    except IntegrityError:
        pass

That will prevent the purposefully-thrown exception from breaking the entire unittest's transaction.

kdazzle

Since @mkoistinen never made his comment, an answer, I'll post his suggestion so people won't have to dig through comments.

consider just declaring your test class as a TransactionTestCase rather than just TestCase.

From the docs: A TransactionTestCase may call commit and rollback and observe the effects of these calls on the database.

If using pytest-django you can pass transaction=True to the django_db decorator to avoid this error.

See https://pytest-django.readthedocs.io/en/latest/database.html#testing-transactions

Django itself has the TransactionTestCase which allows you to test transactions and will flush the database between tests to isolate them. The downside of this is that these tests are much slower to set up due to the required flushing of the database. pytest-django also supports this style of tests, which you can select using an argument to the django_db mark:

@pytest.mark.django_db(transaction=True)
def test_spam():
    pass  # test relying on transactions

For me, the proposed fixes did not work. In my tests, I open some subprocesses with Popen to analyze/lint migrations (e.g. one test checks if there are no model changes).

For me, subclassing from SimpleTestCase instead of TestCase did do the trick.

Note that SimpleTestCase doesn't allow to use the database.

While this does not answer the original question, I hope this helps some people anyway.

I was getting this error on running unit tests in my create_test_data function using django 1.9.7. It worked in earlier versions of django.

It looked like this:

cls.localauth,_ = Organisation.objects.get_or_create(organisation_type=cls.orgtypeLA, name='LA for test', email_general='test@test.com', address='test', postcode='test', telephone='test')
cls.chamber,_ = Organisation.objects.get_or_create(organisation_type=cls.orgtypeC, name='chamber for test', email_general='test@test.com', address='test', postcode='test', telephone='test')
cls.lawfirm,_ = Organisation.objects.get_or_create(organisation_type=cls.orgtypeL, name='lawfirm for test', email_general='test@test.com', address='test', postcode='test', telephone='test')

cls.chamber.active = True
cls.chamber.save()

cls.localauth.active = True
cls.localauth.save()    <---- error here

cls.lawfirm.active = True
cls.lawfirm.save()

My solution was to use update_or_create instead:

cls.localauth,_ = Organisation.objects.update_or_create(organisation_type=cls.orgtypeLA, name='LA for test', email_general='test@test.com', address='test', postcode='test', telephone='test', defaults={'active': True})
cls.chamber,_ = Organisation.objects.update_or_create(organisation_type=cls.orgtypeC, name='chamber for test', email_general='test@test.com', address='test', postcode='test', telephone='test', defaults={'active': True})
cls.lawfirm,_ = Organisation.objects.update_or_create(organisation_type=cls.orgtypeL, name='lawfirm for test', email_general='test@test.com', address='test', postcode='test', telephone='test', defaults={'active': True})

I have the same issue, but with transaction.atomic() and TransactionTestCase didn't work for me.

python manage.py test -r instead of python manage.py test is ok for me, maybe the order of execution is crucial

then i find a doc about Order in which tests are executed, It mentions which test will run first.

So, i use TestCase for database interaction, unittest.TestCase for other simple test, it works now!

The answer of @kdazzle is correct. I didnt try it because people said that 'Django’s TestCase class is a more commonly used subclass of TransactionTestCase' so I thought it was the same use one or another. But the blog of Jahongir Rahmonov explained it better:

the TestCase class wraps the tests within two nested atomic() blocks: one for the whole class and one for each test. This is where TransactionTestCase should be used. It does not wrap the tests with atomic() block and thus you can test your special methods that require a transaction without any problem.

EDIT: It didn't work, I thought yes, but NO.

In 4 years they could fixed this.......................................

Diaa Mohamed Kasem

I had the same issue.

In My Case I was doing this

author.tasks.add(tasks)

so converting it to

author.tasks.add(*tasks)

Removed that error.

标签
python
django
unit-testing
django-signals
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