Issue #18937: Add an assertLogs() context manager to unittest.TestCase to ensure that a block of code emits a message using the logging module.
diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst
index 7a72e0b..380f058 100644
--- 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.
+ .. 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: