Django 原子事务单元测试失败（提交未回滚）

Question

我有一个包含以下两个模型的 Django 项目：

# models.py
from django.db import models, transaction

class Person(models.Model):
    name    = models.TextField()
    surname = models.TextField()

class EmployeeInfo(models.Model):
    person = models.OneToOneField(Person, on_delete=models.CASCADE)
    employee_id = models.TextField(null=True, blank=True)

    @transaction.atomic
    def provision_employee_id(self):
        """Make atomic to ensure that two employees being provisioned at the same time do not get
        the same employee number"""
        self.employee_id = new_employee_number()
        self.save()
        raise Exception("forcing an exception") # Always raise an exception (for testing only)

这是失败的单元测试：

# tests.py
class PersonTestCase(TestCase):
    def test_employee_id_atomic(self):
        person1 = Person(name="John", surname="Doe")
        employee_info = EmployeeInfo(person=person1)
        self.assertIsNone(employee_info.employee_id) # No employee_id yet.
        
        with self.assertRaises(Exception) as context:
            cluster_updated = employee_info.provision_employee_id()

        self.assertIsNone(employee_info.employee_id) # This FAILS

换句话说，即使我将

provision_employee_id()

包装在原子事务中，当引发后续异常时，

save()

也不会回滚。为什么？

Answer 1

这与数据库无关。如果数据库发生故障，它不会回滚 Python 函数，它只会回滚事务中的所有数据库查询。 如果您这样从数据库中获取

Employee

对象，它仍然是

NULL

。如果您在函数中进行了两次

数据库

更改，则这些更改都会回滚。 如果你再次从数据库中获取数据，使用

.refresh_from_db(…)

[Django-doc]^{，你会发现它确实仍然是}NULL:

# tests.py
class PersonTestCase(TestCase):
    def test_employee_id_atomic(self):
        person1 = Person.objects.create(name='John', surname='Doe')
        employee_info = EmployeeInfo.objects.create(person=person1)
        self.assertIsNone(employee_info.employee_id)  # No employee_id yet.

        with self.assertRaises(Exception) as context:
            cluster_updated = employee_info.provision_employee_id()

        employee_info.refresh_from_db()
        self.assertIsNone(employee_info.employee_id)