1 # Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org)
3 # Redistribution and use in source and binary forms, with or without
4 # modification, are permitted provided that the following conditions
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.
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
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17 # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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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.
23 """Supports the unit-testing of logging code.
25 Provides support for unit-testing messages logged using the built-in
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.
38 class TestLogStream(object):
40 """Represents a file-like object for unit-testing logging.
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.
48 def __init__(self, test_case):
49 """Create an instance.
52 test_case: A unittest.TestCase instance.
55 self._test_case = test_case
57 """A list of log messages written to the stream."""
59 # Python documentation says that any object passed to the StreamHandler
60 # constructor should support write() and flush():
62 # http://docs.python.org/library/logging.html#module-logging.handlers
63 def write(self, message):
64 self.messages.append(message)
69 def assertMessages(self, messages):
70 """Assert that the given messages match the logged messages.
72 messages: A list of log message strings.
75 self._test_case.assertEqual(messages, self.messages)
78 class LogTesting(object):
80 """Supports end-to-end unit-testing of log messages.
84 class SampleTest(unittest.TestCase):
87 self._log = LogTesting.setUp(self) # Turn logging on.
90 self._log.tearDown() # Turn off and reset logging.
92 def test_logging_in_some_method(self):
93 call_some_method() # Contains calls to _log.info(), etc.
95 # Check the resulting log messages.
96 self._log.assertMessages(["INFO: expected message #1",
97 "WARNING: expected message #2"])
101 def __init__(self, test_stream, handler):
102 """Create an instance.
104 This method should never be called directly. Instances should
105 instead be created using the static setUp() method.
108 test_stream: A TestLogStream instance.
109 handler: The handler added to the logger.
112 self._test_stream = test_stream
113 self._handler = handler
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()
124 def setUp(test_case, logging_level=logging.INFO):
125 """Configure logging for unit testing.
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--
132 "INFO: This is a test log message."
134 This method should normally be called in the setUp() method
135 of a unittest.TestCase. See the docstring of this class
139 A LogTesting instance.
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.
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)
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
158 logger = LogTesting._getLogger()
159 logger.addHandler(handler)
161 return LogTesting(stream, handler)
164 """Assert there are no remaining log messages, and reset logging.
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.
172 self.assertMessages([])
173 logger = LogTesting._getLogger()
174 logger.removeHandler(self._handler)
177 """Return the current list of log messages."""
178 return self._test_stream.messages
180 # FIXME: Add a clearMessages() method for cases where the caller
181 # deliberately doesn't want to assert every message.
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.
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
193 def assertMessages(self, messages):
194 """Assert the current array of log messages, and clear its contents.
197 messages: A list of log message strings.
201 self._test_stream.assertMessages(messages)
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 = []
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.
215 # FIXME: Rename this class to LoggingTestCaseBase to be sure that
216 # the unittest module does not interpret this class as a unittest
218 class LoggingTestCase(unittest.TestCase):
220 """Supports end-to-end unit-testing of log messages.
224 class SampleTest(LoggingTestCase):
226 def test_logging_in_some_method(self):
227 call_some_method() # Contains calls to _log.info(), etc.
229 # Check the resulting log messages.
230 self.assertLog(["INFO: expected message #1",
231 "WARNING: expected message #2"])
236 self._log = LogTesting.setUp(self)
241 def logMessages(self):
242 """Return the current list of log messages."""
243 return self._log.messages()
245 # FIXME: Add a clearMessages() method for cases where the caller
246 # deliberately doesn't want to assert every message.
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.
255 messages: A list of log message strings.
258 self._log.assertMessages(messages)