Add LoggerFixture

4 files changed, 138 insertions, 0 deletions

diff --git a/lib/fixtures/__init__.py b/lib/fixtures/__init__.py
index 20260d4..fbdd845 100644
--- a/lib/fixtures/__init__.py
+++ b/lib/fixtures/__init__.py
@@ -42,6 +42,7 @@ __all__ = [
     'EnvironmentVariableFixture',
     'Fixture',
     'FunctionFixture',
+    'LoggerFixture',
     'MethodFixture',
     'MonkeyPatch',
     'PackagePathEntry',
@@ -56,6 +57,7 @@ __all__ = [
 from fixtures.fixture import Fixture, FunctionFixture, MethodFixture
 from fixtures._fixtures import (
     EnvironmentVariableFixture,
+    LoggerFixture,
     MonkeyPatch,
     PackagePathEntry,
     PopenFixture,
diff --git a/lib/fixtures/_fixtures/__init__.py b/lib/fixtures/_fixtures/__init__.py
index 6287242..082c936 100644
--- a/lib/fixtures/_fixtures/__init__.py
+++ b/lib/fixtures/_fixtures/__init__.py
@@ -18,6 +18,7 @@
 
 __all__ = [
     'EnvironmentVariableFixture',
+    'LoggerFixture',
     'MonkeyPatch',
     'PackagePathEntry',
     'PopenFixture',
@@ -28,6 +29,7 @@ __all__ = [
 
 
 from fixtures._fixtures.environ import EnvironmentVariableFixture
+from fixtures._fixtures.logger import LoggerFixture
 from fixtures._fixtures.monkeypatch import MonkeyPatch
 from fixtures._fixtures.popen import PopenFixture
 from fixtures._fixtures.packagepath import PackagePathEntry
diff --git a/lib/fixtures/_fixtures/logger.py b/lib/fixtures/_fixtures/logger.py
new file mode 100644
index 0000000..4664c49
--- /dev/null
+++ b/lib/fixtures/_fixtures/logger.py
@@ -0,0 +1,65 @@
+#  fixtures: Fixtures with cleanups for testing and convenience.
+#
+# Copyright (c) 2010, Robert Collins <robertc@robertcollins.net>
+# 
+# Licensed under either the Apache License, Version 2.0 or the BSD 3-clause
+# license at the users choice. A copy of both licenses are available in the
+# project source as Apache-2.0 and BSD. You may not use this file except in
+# compliance with one of these two licences.
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under these licenses is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# license you chose for the specific language governing permissions and
+# limitations under that license.
+from logging import StreamHandler, getLogger, INFO, Formatter
+from cStringIO import StringIO
+
+from fixtures import Fixture
+
+__all__ = [
+    'LoggerFixture',
+    ]
+
+
+class LoggerFixture(Fixture):
+    """Replace a logger and restore it upon cleanup.
+
+    :param name: Optionally, the name of the logger to replace.
+    :param level: Optionally, the log level to set.
+    :param format: Optionally, the format the logger should use.
+
+    Example:
+
+      def test_log(self)
+          fixture = self.useFixture(LoggerFixture())
+          logging.info('message')
+          self.assertEqual('message', fixture.output)
+    """
+
+    def __init__(self, name="", level=INFO, format=""):
+        super(LoggerFixture, self).__init__()
+        self._name = name
+        self._level = level
+        self._format = format
+
+    def setUp(self):
+        super(LoggerFixture, self).setUp()
+        self._output = StringIO()
+        self._handler = StreamHandler(self._output)
+        self._logger = getLogger(self._name)
+        self._logger.addHandler(self._handler)
+
+        if self._format:
+            self._handler.setFormatter(Formatter(self._format))
+
+        self._old_level = self._logger.level
+        if self._level:
+            self._logger.setLevel(self._level)
+
+        self.addCleanup(self._logger.removeHandler, self._handler)
+        self.addCleanup(self._logger.setLevel, self._old_level)
+
+    @property
+    def output(self):
+        return self._output.getvalue()
diff --git a/lib/fixtures/tests/_fixtures/test_logger.py b/lib/fixtures/tests/_fixtures/test_logger.py
new file mode 100644
index 0000000..f628633
--- /dev/null
+++ b/lib/fixtures/tests/_fixtures/test_logger.py
@@ -0,0 +1,69 @@
+#  fixtures: Fixtures with cleanups for testing and convenience.
+#
+# Copyright (c) 2011, Robert Collins <robertc@robertcollins.net>
+# 
+# Licensed under either the Apache License, Version 2.0 or the BSD 3-clause
+# license at the users choice. A copy of both licenses are available in the
+# project source as Apache-2.0 and BSD. You may not use this file except in
+# compliance with one of these two licences.
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under these licenses is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# license you chose for the specific language governing permissions and
+# limitations under that license.
+
+import logging
+
+from testtools import TestCase
+from cStringIO import StringIO
+
+from fixtures import LoggerFixture, TestWithFixtures
+
+
+class LoggerFixtureTest(TestCase, TestWithFixtures):
+
+    def setUp(self):
+        super(LoggerFixtureTest, self).setUp()
+        # Silence the default sysout logger
+        self.handler = logging.StreamHandler(StringIO())
+        self.logger = logging.getLogger()
+        self.logger.addHandler(self.handler)
+
+    def tearDown(self):
+        super(LoggerFixtureTest, self).tearDown()
+        # Restore the default sysout logger
+        self.logger.removeHandler(self.handler)
+
+    def test_output(self):
+        """The L{LoggerFixture.output} property returns the logging output."""
+        fixture = LoggerFixture()
+        self.useFixture(fixture)
+        logging.info("some message")
+        self.assertEqual("some message\n", fixture.output)
+
+    def test_replace_and_restore_logger(self):
+        """The logger is replaced upon setup and restored upon cleanup."""
+        fixture = LoggerFixture()
+        logging.info("first message")
+        with fixture:
+            logging.info("second message")
+        logging.info("third message")
+        self.assertEqual("second message\n", fixture.output)
+
+    def test_restore_level(self):
+        """The original logging level is restored at cleanup."""
+        self.logger.setLevel(logging.DEBUG)
+        fixture = LoggerFixture(level=logging.WARNING)
+        with fixture:
+            # The fixture won't capture this, because the DEBUG level
+            # is lower than the WARNING one
+            logging.debug("debug message")
+        self.assertEqual("", fixture.output)
+
+    def test_format(self):
+        """It's possible to set an alternate format for the logger."""
+        fixture = LoggerFixture(format="%(module)s")
+        self.useFixture(fixture)
+        logging.info("message")
+        self.assertEqual("test_logger\n", fixture.output)