[Python-Dev] [Python-checkins] cpython: Issue #18937: Add an assertLogs() context manager to unittest.TestCase to (original) (raw)

Terry Reedy tjreedy at udel.edu
Sat Sep 14 20:14:10 CEST 2013

On 9/14/2013 1:45 PM, antoine.pitrou wrote:

http://hg.python.org/cpython/rev/4f5815747f58 changeset: 85701:4f5815747f58 user: Antoine Pitrou <solipsis at pitrou.net> date: Sat Sep 14 19:45:47 2013 +0200 summary: Issue #18937: Add an assertLogs() context manager to unittest.TestCase to ensure that a block of code emits a message using the logging module.

files: Doc/library/unittest.rst | 41 +++++++ Lib/unittest/case.py | 109 +++++++++++++++++++- Lib/unittest/test/testcase.py | 96 ++++++++++++++++++ Misc/NEWS | 2 + 4 files changed, 242 insertions(+), 6 deletions(-)

diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst --- a/Doc/library/unittest.rst +++ b/Doc/library/unittest.rst @@ -1031,6 +1031,47 @@ .. versionchanged:: 3.3 Added the msg keyword argument when used as a context manager.

assertWarnsRegex

+ .. method:: assertLogs(logger=None, level=None) + + A context manager to test that at least one message is logged on + the logger or one of its children, with at least the given + level. + + If given, logger should be a :class:logging.Logger object or a + :class:str giving the name of a logger. The default is the root + logger, which will catch all messages. + + If given, level should be either a numeric logging level or + its string equivalent (for example either "ERROR" or + :attr:logging.ERROR). The default is :attr:logging.INFO. + + The test passes if at least one message emitted inside the with + block matches the logger and level conditions, otherwise it fails. + + The object returned by the context manager is a recording helper + which keeps tracks of the matching log messages. It has two + attributes: + + .. attribute:: records + + A list of :class:logging.LogRecord objects of the matching + log messages. + + .. attribute:: output + + A list of :class:str objects with the formatted output of + matching messages. + + Example:: + + with self.assertLogs('foo', level='INFO') as cm: + logging.getLogger('foo').info('first message') + logging.getLogger('foo.bar').error('second message') + self.assertEqual(cm.output, ['INFO:foo:first message', + 'ERROR:foo.bar:second message']) + + .. versionadded:: 3.4 +

There are also other methods used to perform more specific checks, such as:

The new method should be added to the table of raises/warns methods that starts this group. The table intro sentence

"It is also possible to check that exceptions and warnings are raised using the following methods:"

should be modified to something like

"It is also possible to check the production of exception, warning, and log messages using the following methods:"

Terry

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