python - 特定のログメッセージがDjangoテストケースに記録されているかどうかをテストするにはどうすればよいですか？

Question

コード内の特定の条件により、ログメッセージがdjangoログに書き込まれるようにしたいです。Djangoユニットテストフレームワークでこれをどのように行うのですか？

送信メールを確認するのと同じように、ログに記録されたメッセージを確認できる場所はありますか？私の単体テストは拡張されdjango.test.TestCaseます。

Answer 1

モジュールを使用しmockて、ロギング モジュールまたはロガー オブジェクトをモックします。それが終わったら、ロギング関数が呼び出される引数を確認してください。

たとえば、次のようにコーディングするとします。

import logging

logger = logging.getLogger('my_logger')

logger.error("Your log message here")

次のようになります。

from unittest.mock import patch # For python 2.x use from mock import patch

@patch('this.is.my.module.logger')
def test_check_logging_message(self, mock_logger):
    mock_logger.error.assert_called_with("Your log message here")

Answer 2

The common way of mocking out the logger object (see the splendid chap Simeon Visser's answer) is slightly tricky in that it requires the test to mock out the logging in all the places it's done. This is awkward if the logging comes from more than one module, or is in code you don't own. If the module the logging comes from changes name, it will break your tests.

The splendid 'testfixtures' package includes tools to add a logging handler which captures all generated log messages, no matter where they come from. The captured messages can later be interrogated by the test. In its simplest form:

Assuming code-under-test, which logs:

import logging
logger = logging.getLogger()
logger.info('a message')
logger.error('an error')

A test for this would be:

from testfixtures import LogCapture
with LogCapture() as l:
    call_code_under_test()
l.check(
    ('root', 'INFO', 'a message'),
    ('root', 'ERROR', 'an error'),
)

The word 'root' indicates the logging was sent via a logger created using logging.getLogger() (i.e. with no args.) If you pass an arg to getLogger (__name__ is conventional), that arg will be used in place of 'root'.

The test does not care what module created the logging. It could be a sub-module called by our code-under-test, including 3rd party code.

The test asserts about the actual log message that was generated, as opposed to the technique of mocking, which asserts about the args that were passed. These will differ if the logging.info call uses '%s' format strings with additional arguments that you don't expand yourself (e.g. use logging.info('total=%s', len(items)) instead of logging.info('total=%s' % len(items)), which you should. It's no extra work, and allows hypothetical future logging aggregation services such as 'Sentry' to work properly - they can see that "total=12" and "total=43" are two instances of the same log message. That's the reason why pylint warns about the latter form of logging.info call.)

LogCapture includes facilities for log filtering and the like. Its parent 'testfixtures' package, written by Chris Withers, another splendid chap, includes many other useful testing tools. Documentation is here: http://pythonhosted.org/testfixtures/logging.html

Answer 3

テスト クラスを使用している場合は、次のソリューションを使用できます。

import logger

from django.test import TestCase


class MyTest(TestCase):
    @classmethod
    def setUpClass(cls):
        super(MyTest, cls).setUpClass()
        cls.logging_error = logging.error
        logging.error = cls._error_log

    @classmethod
    def tearDownClass(cls):
        super(MyTest, cls).tearDownClass()
        logging.error = cls.logging_error

    @classmethod
    def _error_log(cls, msg):
      cls.logger = msg

    def test_logger(self):
        self.assertIn('Message', self.logger)

errorこのメソッドは、モジュールの関数loggingをテスト目的でのみカスタム メソッドに置き換え、stdout をcls.logger変数に入れます。この変数は、 を呼び出してすべてのテスト ケースで使用できますself.logger。最後に、error関数をloggingモジュールから元に戻すことにより、変更を元に戻します。