Allow ``OS_DEBUG`` environment variable to specify log level.

Preserve original behavior when ``OS_DEBUG`` is ``True``, but if variable
is set to a valid log level, such as 'WARNING' use that level instead to
allow finer grained control over verbosity of log messages with the
FakeLogger.

Change-Id: I6594cec8de6fa221fe81f663a9126b2df8762ef3
Closes-Bug: 1280454

3 files changed, 29 insertions, 5 deletions

diff --git a/oslotest/base.py b/oslotest/base.py
index b77f846..cdea425 100644
--- a/oslotest/base.py
+++ b/oslotest/base.py
@@ -45,7 +45,8 @@ class BaseTestCase(testtools.TestCase):
     it produces.
 
     If the environment variable ``OS_DEBUG`` is set to a true value,
-    debug logging is enabled.
+    debug logging is enabled. Alternatively, the ``OS_DEBUG``
+    environment variable can be set to a valid log level.
 
     If the environment variable ``OS_LOG_CAPTURE`` is set to a true
     value, a logging fixture is installed to capture the log output.
diff --git a/oslotest/log.py b/oslotest/log.py
index 9435e18..94627d9 100644
--- a/oslotest/log.py
+++ b/oslotest/log.py
@@ -16,6 +16,8 @@ import os
 import fixtures
 
 _TRUE_VALUES = ('True', 'true', '1', 'yes')
+_FALSE_VALUES = ('False', 'false', '0', 'no')
+_LOG_LEVELS = ('DEBUG', 'INFO', 'WARN', 'WARNING', 'ERROR', 'CRITICAL')
 
 
 class ConfigureLogging(fixtures.Fixture):
@@ -23,9 +25,12 @@ class ConfigureLogging(fixtures.Fixture):
 
     The behavior is managed through two environment variables. If
     ``OS_DEBUG`` is true then the logging level is set to debug. If
-    ``OS_LOG_CAPTURE`` is true a FakeLogger is configured.
+    ``OS_LOG_CAPTURE`` is true a FakeLogger is configured. Alternatively,
+    ``OS_DEBUG`` can be set to an explicit log level, such as ``INFO``.
 
-    "True" values include ``True``, ``true``, ``1``, and ``yes``.
+    "True" values include ``True``, ``true``, ``1`` and ``yes``.
+    Valid log levels include ``DEBUG``, ``INFO``, ``WARNING``, ``ERROR``
+    and ``CRITICAL``.
 
     .. py:attribute:: logger
 
@@ -34,7 +39,7 @@ class ConfigureLogging(fixtures.Fixture):
     .. py:attribute:: level
 
        ``logging.DEBUG`` if debug logging is enabled, otherwise
-       ``None``.
+       the log level specified by ``OS_DEBUG``, otherwise ``None``.
 
     :param format: The logging format string to use.
 
@@ -47,8 +52,13 @@ class ConfigureLogging(fixtures.Fixture):
         super(ConfigureLogging, self).__init__()
         self._format = format
         self.level = None
-        if os.environ.get('OS_DEBUG') in _TRUE_VALUES:
+        _os_debug = os.environ.get('OS_DEBUG')
+        if _os_debug in _TRUE_VALUES:
             self.level = logging.DEBUG
+        elif _os_debug in _LOG_LEVELS:
+            self.level = getattr(logging, _os_debug)
+        elif _os_debug and _os_debug not in _FALSE_VALUES:
+            raise ValueError('OS_DEBUG=%s is invalid.' % (_os_debug))
         self.capture_logs = os.environ.get('OS_LOG_CAPTURE') in _TRUE_VALUES
         self.logger = None
 
diff --git a/tests/unit/test_log.py b/tests/unit/test_log.py
index e87cd0e..6a00337 100644
--- a/tests/unit/test_log.py
+++ b/tests/unit/test_log.py
@@ -50,6 +50,19 @@ class ConfigureLoggingTestCase(testtools.TestCase):
             level=logging.DEBUG)
 
     @mock.patch('os.environ.get')
+    @mock.patch('logging.basicConfig')
+    def test_fake_logs_with_warning(self, basic_logger_mock, env_get_mock):
+        env_get_mock.side_effect = lambda value, default=None: {
+            'OS_DEBUG': 'WARNING', 'OS_LOG_CAPTURE': 0}.get(value, default)
+        f = log.ConfigureLogging()
+        f.setUp()
+        env_get_mock.assert_any_call('OS_LOG_CAPTURE')
+        env_get_mock.assert_any_calls('OS_DEBUG')
+        basic_logger_mock.assert_called_once_with(
+            format=log.ConfigureLogging.DEFAULT_FORMAT,
+            level=logging.WARNING)
+
+    @mock.patch('os.environ.get')
     def test_fake_logs_with_log_capture(self, env_get_mock):
         env_get_mock.side_effect = lambda value: {'OS_DEBUG': 0,
                                                   'OS_LOG_CAPTURE': 'True'