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Diffstat (limited to 'Tools/Scripts/webkitpy/common/system/logtesting.py')
| -rw-r--r-- | Tools/Scripts/webkitpy/common/system/logtesting.py | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/Tools/Scripts/webkitpy/common/system/logtesting.py b/Tools/Scripts/webkitpy/common/system/logtesting.py new file mode 100644 index 0000000..e361cb5 --- /dev/null +++ b/Tools/Scripts/webkitpy/common/system/logtesting.py @@ -0,0 +1,258 @@ +# Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org) +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions +# are met: +# 1. Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# 2. Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED +# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE +# DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR +# ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR +# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +"""Supports the unit-testing of logging code. + +Provides support for unit-testing messages logged using the built-in +logging module. + +Inherit from the LoggingTestCase class for basic testing needs. For +more advanced needs (e.g. unit-testing methods that configure logging), +see the TestLogStream class, and perhaps also the LogTesting class. + +""" + +import logging +import unittest + + +class TestLogStream(object): + + """Represents a file-like object for unit-testing logging. + + This is meant for passing to the logging.StreamHandler constructor. + Log messages captured by instances of this object can be tested + using self.assertMessages() below. + + """ + + def __init__(self, test_case): + """Create an instance. + + Args: + test_case: A unittest.TestCase instance. + + """ + self._test_case = test_case + self.messages = [] + """A list of log messages written to the stream.""" + + # Python documentation says that any object passed to the StreamHandler + # constructor should support write() and flush(): + # + # http://docs.python.org/library/logging.html#module-logging.handlers + def write(self, message): + self.messages.append(message) + + def flush(self): + pass + + def assertMessages(self, messages): + """Assert that the given messages match the logged messages. + + messages: A list of log message strings. + + """ + self._test_case.assertEquals(messages, self.messages) + + +class LogTesting(object): + + """Supports end-to-end unit-testing of log messages. + + Sample usage: + + class SampleTest(unittest.TestCase): + + def setUp(self): + self._log = LogTesting.setUp(self) # Turn logging on. + + def tearDown(self): + self._log.tearDown() # Turn off and reset logging. + + def test_logging_in_some_method(self): + call_some_method() # Contains calls to _log.info(), etc. + + # Check the resulting log messages. + self._log.assertMessages(["INFO: expected message #1", + "WARNING: expected message #2"]) + + """ + + def __init__(self, test_stream, handler): + """Create an instance. + + This method should never be called directly. Instances should + instead be created using the static setUp() method. + + Args: + test_stream: A TestLogStream instance. + handler: The handler added to the logger. + + """ + self._test_stream = test_stream + self._handler = handler + + @staticmethod + def _getLogger(): + """Return the logger being tested.""" + # It is possible we might want to return something other than + # the root logger in some special situation. For now, the + # root logger seems to suffice. + return logging.getLogger() + + @staticmethod + def setUp(test_case, logging_level=logging.INFO): + """Configure logging for unit testing. + + Configures the root logger to log to a testing log stream. + Only messages logged at or above the given level are logged + to the stream. Messages logged to the stream are formatted + in the following way, for example-- + + "INFO: This is a test log message." + + This method should normally be called in the setUp() method + of a unittest.TestCase. See the docstring of this class + for more details. + + Returns: + A LogTesting instance. + + Args: + test_case: A unittest.TestCase instance. + logging_level: An integer logging level that is the minimum level + of log messages you would like to test. + + """ + stream = TestLogStream(test_case) + handler = logging.StreamHandler(stream) + handler.setLevel(logging_level) + formatter = logging.Formatter("%(levelname)s: %(message)s") + handler.setFormatter(formatter) + + # Notice that we only change the root logger by adding a handler + # to it. In particular, we do not reset its level using + # logger.setLevel(). This ensures that we have not interfered + # with how the code being tested may have configured the root + # logger. + logger = LogTesting._getLogger() + logger.addHandler(handler) + + return LogTesting(stream, handler) + + def tearDown(self): + """Assert there are no remaining log messages, and reset logging. + + This method asserts that there are no more messages in the array of + log messages, and then restores logging to its original state. + This method should normally be called in the tearDown() method of a + unittest.TestCase. See the docstring of this class for more details. + + """ + self.assertMessages([]) + logger = LogTesting._getLogger() + logger.removeHandler(self._handler) + + def messages(self): + """Return the current list of log messages.""" + return self._test_stream.messages + + # FIXME: Add a clearMessages() method for cases where the caller + # deliberately doesn't want to assert every message. + + # We clear the log messages after asserting since they are no longer + # needed after asserting. This serves two purposes: (1) it simplifies + # the calling code when we want to check multiple logging calls in a + # single test method, and (2) it lets us check in the tearDown() method + # that there are no remaining log messages to be asserted. + # + # The latter ensures that no extra log messages are getting logged that + # the caller might not be aware of or may have forgotten to check for. + # This gets us a bit more mileage out of our tests without writing any + # additional code. + def assertMessages(self, messages): + """Assert the current array of log messages, and clear its contents. + + Args: + messages: A list of log message strings. + + """ + try: + self._test_stream.assertMessages(messages) + finally: + # We want to clear the array of messages even in the case of + # an Exception (e.g. an AssertionError). Otherwise, another + # AssertionError can occur in the tearDown() because the + # array might not have gotten emptied. + self._test_stream.messages = [] + + +# This class needs to inherit from unittest.TestCase. Otherwise, the +# setUp() and tearDown() methods will not get fired for test case classes +# that inherit from this class -- even if the class inherits from *both* +# unittest.TestCase and LoggingTestCase. +# +# FIXME: Rename this class to LoggingTestCaseBase to be sure that +# the unittest module does not interpret this class as a unittest +# test case itself. +class LoggingTestCase(unittest.TestCase): + + """Supports end-to-end unit-testing of log messages. + + Sample usage: + + class SampleTest(LoggingTestCase): + + def test_logging_in_some_method(self): + call_some_method() # Contains calls to _log.info(), etc. + + # Check the resulting log messages. + self.assertLog(["INFO: expected message #1", + "WARNING: expected message #2"]) + + """ + + def setUp(self): + self._log = LogTesting.setUp(self) + + def tearDown(self): + self._log.tearDown() + + def logMessages(self): + """Return the current list of log messages.""" + return self._log.messages() + + # FIXME: Add a clearMessages() method for cases where the caller + # deliberately doesn't want to assert every message. + + # See the code comments preceding LogTesting.assertMessages() for + # an explanation of why we clear the array of messages after + # asserting its contents. + def assertLog(self, messages): + """Assert the current array of log messages, and clear its contents. + + Args: + messages: A list of log message strings. + + """ + self._log.assertMessages(messages) |