1 # Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org)

     2 #

     3 # Redistribution and use in source and binary forms, with or without

     4 # modification, are permitted provided that the following conditions

     5 # are met:

     6 # 1.  Redistributions of source code must retain the above copyright

     7 #     notice, this list of conditions and the following disclaimer.

     8 # 2.  Redistributions in binary form must reproduce the above copyright

     9 #     notice, this list of conditions and the following disclaimer in the

    10 #     documentation and/or other materials provided with the distribution.

    11 #

    12 # THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND

    13 # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

    14 # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

    15 # DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR

    16 # ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

    17 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

    18 # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER

    19 # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

    20 # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

    21 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    22 

    23 """Supports the unit-testing of logging code.

    24 

    25 Provides support for unit-testing messages logged using the built-in

    26 logging module.

    27 

    28 Inherit from the LoggingTestCase class for basic testing needs.  For

    29 more advanced needs (e.g. unit-testing methods that configure logging),

    30 see the TestLogStream class, and perhaps also the LogTesting class.

    31 

    32 """

    33 

    34 import logging

    35 import unittest

    36 

    37 

    38 class TestLogStream(object):

    39 

    40     """Represents a file-like object for unit-testing logging.

    41 

    42     This is meant for passing to the logging.StreamHandler constructor.

    43     Log messages captured by instances of this object can be tested

    44     using self.assertMessages() below.

    45 

    46     """

    47 

    48     def __init__(self, test_case):

    49         """Create an instance.

    50 

    51         Args:

    52           test_case: A unittest.TestCase instance.

    53 

    54         """

    55         self._test_case = test_case

    56         self.messages = []

    57         """A list of log messages written to the stream."""

    58 

    59     # Python documentation says that any object passed to the StreamHandler

    60     # constructor should support write() and flush():

    61     #

    62     # http://docs.python.org/library/logging.html#module-logging.handlers

    63     def write(self, message):

    64         self.messages.append(message)

    65 

    66     def flush(self):

    67         pass

    68 

    69     def assertMessages(self, messages):

    70         """Assert that the given messages match the logged messages.

    71 

    72         messages: A list of log message strings.

    73 

    74         """

    75         self._test_case.assertEquals(messages, self.messages)

    76 

    77 

    78 class LogTesting(object):

    79 

    80     """Supports end-to-end unit-testing of log messages.

    81 

    82         Sample usage:

    83 

    84           class SampleTest(unittest.TestCase):

    85 

    86               def setUp(self):

    87                   self._log = LogTesting.setUp(self)  # Turn logging on.

    88 

    89               def tearDown(self):

    90                   self._log.tearDown()  # Turn off and reset logging.

    91 

    92               def test_logging_in_some_method(self):

    93                   call_some_method()  # Contains calls to _log.info(), etc.

    94 

    95                   # Check the resulting log messages.

    96                   self._log.assertMessages(["INFO: expected message #1",

    97                                           "WARNING: expected message #2"])

    98 

    99     """

   100 

   101     def __init__(self, test_stream, handler):

   102         """Create an instance.

   103 

   104         This method should never be called directly.  Instances should

   105         instead be created using the static setUp() method.

   106 

   107         Args:

   108           test_stream: A TestLogStream instance.

   109           handler: The handler added to the logger.

   110 

   111         """

   112         self._test_stream = test_stream

   113         self._handler = handler

   114 

   115     @staticmethod

   116     def _getLogger():

   117         """Return the logger being tested."""

   118         # It is possible we might want to return something other than

   119         # the root logger in some special situation.  For now, the

   120         # root logger seems to suffice.

   121         return logging.getLogger()

   122 

   123     @staticmethod

   124     def setUp(test_case, logging_level=logging.INFO):

   125         """Configure logging for unit testing.

   126 

   127         Configures the root logger to log to a testing log stream.

   128         Only messages logged at or above the given level are logged

   129         to the stream.  Messages logged to the stream are formatted

   130         in the following way, for example--

   131 

   132         "INFO: This is a test log message."

   133 

   134         This method should normally be called in the setUp() method

   135         of a unittest.TestCase.  See the docstring of this class

   136         for more details.

   137 

   138         Returns:

   139           A LogTesting instance.

   140 

   141         Args:

   142           test_case: A unittest.TestCase instance.

   143           logging_level: An integer logging level that is the minimum level

   144                          of log messages you would like to test.

   145 

   146         """

   147         stream = TestLogStream(test_case)

   148         handler = logging.StreamHandler(stream)

   149         handler.setLevel(logging_level)

   150         formatter = logging.Formatter("%(levelname)s: %(message)s")

   151         handler.setFormatter(formatter)

   152 

   153         # Notice that we only change the root logger by adding a handler

   154         # to it.  In particular, we do not reset its level using

   155         # logger.setLevel().  This ensures that we have not interfered

   156         # with how the code being tested may have configured the root

   157         # logger.

   158         logger = LogTesting._getLogger()

   159         logger.addHandler(handler)

   160 

   161         return LogTesting(stream, handler)

   162 

   163     def tearDown(self):

   164         """Assert there are no remaining log messages, and reset logging.

   165 

   166         This method asserts that there are no more messages in the array of

   167         log messages, and then restores logging to its original state.

   168         This method should normally be called in the tearDown() method of a

   169         unittest.TestCase.  See the docstring of this class for more details.

   170 

   171         """

   172         self.assertMessages([])

   173         logger = LogTesting._getLogger()

   174         logger.removeHandler(self._handler)

   175 

   176     def messages(self):

   177         """Return the current list of log messages."""

   178         return self._test_stream.messages

   179 

   180     # FIXME: Add a clearMessages() method for cases where the caller

   181     #        deliberately doesn't want to assert every message.

   182 

   183     # We clear the log messages after asserting since they are no longer

   184     # needed after asserting.  This serves two purposes: (1) it simplifies

   185     # the calling code when we want to check multiple logging calls in a

   186     # single test method, and (2) it lets us check in the tearDown() method

   187     # that there are no remaining log messages to be asserted.

   188     #

   189     # The latter ensures that no extra log messages are getting logged that

   190     # the caller might not be aware of or may have forgotten to check for.

   191     # This gets us a bit more mileage out of our tests without writing any

   192     # additional code.

   193     def assertMessages(self, messages):

   194         """Assert the current array of log messages, and clear its contents.

   195 

   196         Args:

   197           messages: A list of log message strings.

   198 

   199         """

   200         try:

   201             self._test_stream.assertMessages(messages)

   202         finally:

   203             # We want to clear the array of messages even in the case of

   204             # an Exception (e.g. an AssertionError).  Otherwise, another

   205             # AssertionError can occur in the tearDown() because the

   206             # array might not have gotten emptied.

   207             self._test_stream.messages = []

   208 

   209 

   210 # This class needs to inherit from unittest.TestCase.  Otherwise, the

   211 # setUp() and tearDown() methods will not get fired for test case classes

   212 # that inherit from this class -- even if the class inherits from *both*

   213 # unittest.TestCase and LoggingTestCase.

   214 #

   215 # FIXME: Rename this class to LoggingTestCaseBase to be sure that

   216 #        the unittest module does not interpret this class as a unittest

   217 #        test case itself.

   218 class LoggingTestCase(unittest.TestCase):

   219 

   220     """Supports end-to-end unit-testing of log messages.

   221 

   222         Sample usage:

   223 

   224           class SampleTest(LoggingTestCase):

   225 

   226               def test_logging_in_some_method(self):

   227                   call_some_method()  # Contains calls to _log.info(), etc.

   228 

   229                   # Check the resulting log messages.

   230                   self.assertLog(["INFO: expected message #1",

   231                                   "WARNING: expected message #2"])

   232 

   233     """

   234 

   235     def setUp(self):

   236         self._log = LogTesting.setUp(self)

   237 

   238     def tearDown(self):

   239         self._log.tearDown()

   240 

   241     def logMessages(self):

   242         """Return the current list of log messages."""

   243         return self._log.messages()

   244 

   245     # FIXME: Add a clearMessages() method for cases where the caller

   246     #        deliberately doesn't want to assert every message.

   247 

   248     # See the code comments preceding LogTesting.assertMessages() for

   249     # an explanation of why we clear the array of messages after

   250     # asserting its contents.

   251     def assertLog(self, messages):

   252         """Assert the current array of log messages, and clear its contents.

   253 

   254         Args:

   255           messages: A list of log message strings.

   256 

   257         """

   258         self._log.assertMessages(messages)