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

Question

I am getting `TransactionManagementError` when trying to save a Django User model instance and in its `post_save` signal, I'm saving some models that have the user as the foreign key. The context and error is pretty similar to this question django TransactionManagementError when using signals However, in this case, the error occurs only while unit testing. It works well in manual testing, but unit tests fails. Is there anything that I'm missing? Here are the code snippets: views.py ``` @csrf_exempt def mobileRegister(request): if request.method == 'GET': response = {"error": "GET request not accepted!!"} return HttpResponse(json.dumps(response), content_type="application/json",status=500) elif request.method == 'POST': postdata = json.loads(request.body) try: # Get POST data which is to be used to save the user username = postdata.get('phone') password = postdata.get('password') email = postdata.get('email',"") first_name = postdata.get('first_name',"") last_name = postdata.get('last_…

Accepted Answer

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.

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

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