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

[Terry Reedy]

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/test_case.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