Django BaseCommand属性错误：自定义命令测试报AttributeError

我跟着教程开发Django项目，教程代码能正常运行，但我的代码出问题了。我编写了一个等待数据库就绪的自定义命令，同时写了对应的测试用例，运行测试时触发了AttributeError。

自定义命令代码（wait_for_db.py） #

import time
from psycopg2 import OperationalError as Psycopg2OpError
from django.db.utils import OperationalError
from django.core.management.base import BaseCommand, CommandError

class Command(BaseCommand):

    def handle(self, *args, **options):
        self.stdout.write('waiting for database...')

        db_up = False
        while db_up is False:
            try:
                self.check(databases=['default'])
                db_up = True
            except(Psycopg2OpError, OperationalError):
                self.stdout.write("Database unavailable, waiting 1 second...")
                time.sleep(1)
        
        self.stdout.write(self.style.SUCCESS('Database available!'))

测试用例代码（test_command.py） #

from unittest.mock import patch

from psycopg2 import OperationalError as Psycopg2OpError

from django.core.management import call_command
from django.db.utils import OperationalError
from django.test import SimpleTestCase

@patch('core.management.commands.wait_for_db.Command.Check')
class CommandTests(SimpleTestCase):

    def test_wait_for_db_ready(self, patched_check):
        """测试数据库就绪时的等待逻辑"""
        patched_check.return_value = True

        call_command('wait_for_db')

        patched_check.assert_called_once_with(databases=['default'])

    @patch('time.sleep')
    def test_wait_for_db_delay(self, patched_sleep, patched_check):
        """测试数据库不可用时的等待重试逻辑"""
        patched_check.side_effect = [Psycopg2OpError] * 2 + \
            [OperationalError] * 3 + [True]

        call_command('wait_for_db')
        self.assertEqual(patched_check.call_count, 6)
        patched_check.assert_called_with(databases=['default'])

报错信息 #

AttributeError: <class 'core.management.commands.wait_for_db.Command'> does not have the attribute 'Check'

文件结构 #

修复方案 #

问题根源是测试用例的patch路径错误：

• 代码中调用的是实例方法self.check（小写c），但你在patch时写的是Command.Check（大写C），该类本身没有名为Check的属性。

修改测试用例的patch装饰器，将路径改为正确的实例方法路径：

@patch('core.management.commands.wait_for_db.Command.check')

修改后重新运行测试，该错误即可解决。

内容的提问来源于stack exchange，提问作者The Bat