Same problem as in https://code.djangoproject.com/ticket/11665. Though I hope it will be fixed soon in here :)
Is this postgres-specific?
I would not mind having test case, as I don't use postgres nowadays...
This should affect any database with deferred constraints.
Brief test case:
parent = models.OneToOneField(Parent, primary_key=True)
p = Parent(pk=1)
c = Child(parent=p)
# This should raise IntegrityError
It actually raises IntergrityError if you use DestructiveDatabaseTestCase