diff --git a/tests/test_logger_keywords.py b/tests/test_logger_keywords.py
new file mode 100644
index 0000000..74265b8
--- /dev/null
+++ b/tests/test_logger_keywords.py
@@ -0,0 +1,175 @@
+# -*- coding: utf-8 -*-
+"""
+Unit tests for Flask-Logging-Extras
+"""
+
+import logging
+import sys
+from unittest import TestCase
+
+from flask import Flask
+
+import flask_logging_extras
+
+class ListStream(object):
+    """
+    Primitive stream that stores its input lines in a list
+    """
+
+    def __init__(self, *args, **kwargs):
+        self.lines = []
+
+        super(ListStream, self).__init__(*args, **kwargs)
+
+    def write(self, data):
+        if len(self.lines) == 0 or self.lines[-1].endswith('\n'):
+            self.lines.append(data)
+        else:
+            self.lines[-1] += data
+
+
+class TestingStreamHandler(logging.StreamHandler):
+    def handleError(self, record):
+        exc, exc_msg, trace = sys.exc_info()
+
+        super(logging.StreamHandler, self).handleError(record)
+
+        raise(exc(exc_msg))
+
+
+class LoggerKeywordsTestCase(TestCase):
+    def setUp(self):
+        self.original_logger_class = logging.getLoggerClass()
+
+    def tearDown(self):
+        logging.setLoggerClass(self.original_logger_class)
+
+    def test_logger_registration(self):
+        class NotLoggerClass(object):
+            pass
+
+        with self.assertRaises(TypeError):
+            flask_logging_extras.register_logger_class(cls=NotLoggerClass)
+
+        original_logging_class = logging.getLoggerClass()
+
+        old_class = flask_logging_extras.register_logger_class()
+
+        # If no class is specified, FlaskExtraLogger should be registered
+        self.assertEqual(logging.getLoggerClass(),
+                         flask_logging_extras.FlaskExtraLogger)
+        # The return value of this function should be the old default
+        self.assertEqual(original_logging_class, old_class)
+
+        class MyLogger(logging.Logger):
+            pass
+
+        # Calling register_logger_class() with any subclass of
+        # logging.Logger should succeed
+        flask_logging_extras.register_logger_class(cls=MyLogger)
+
+    def test_logger_class(self):
+        # If app is present during __init__, and is not None, we should get
+        # a TypeError
+        with self.assertRaises(TypeError):
+            flask_logging_extras.FlaskExtraLogger('test_logger',
+                                                  app='test value')
+
+        # If app is present, but is None, no exception should be raised
+        flask_logging_extras.FlaskExtraLogger('test_logger', app=None)
+
+    def test_logger_class_init_app(self):
+        logger = flask_logging_extras.FlaskExtraLogger('test')
+        app = Flask('test_app')
+
+        logger.init_app(app)
+
+        self.assertEqual({}, logger._valid_keywords)
+
+        app.config['FLASK_LOGGING_EXTRAS_KEYWORDS'] = {'exc_info': None}
+
+        with self.assertRaises(ValueError):
+            logger.init_app(app)
+
+        app.config['FLASK_LOGGING_EXTRAS_KEYWORDS'] = {'my_keyword': '<unset>'}
+
+        logger.init_app(app)
+        self.assertEqual({'my_keyword': '<unset>'}, logger._valid_keywords)
+
+        # Without registration first, app.logger should not be of class
+        # FlaskExtraLogger (even though logger.init_app() succeeded without
+        # it.)
+        self.assertNotIsInstance(app.logger,
+                                 flask_logging_extras.FlaskExtraLogger)
+
+        flask_logging_extras.register_logger_class()
+
+        # Even after registratiiion, existing apps are (obviously) not
+        # tampered with
+
+        self.assertNotIsInstance(app.logger,
+                                 flask_logging_extras.FlaskExtraLogger)
+
+        app = Flask('test_app')
+
+        # Newly created apps, though, should be made with this class
+        self.assertIsInstance(app.logger,
+                              flask_logging_extras.FlaskExtraLogger)
+
+    def _create_app_with_logger(self, fmt, keywords=[]):
+        app = Flask('test_app')
+
+        self.assertIsInstance(app.logger,
+                              flask_logging_extras.FlaskExtraLogger)
+
+        app.config['FLASK_LOGGING_EXTRAS_KEYWORDS'] = keywords
+        app.logger.init_app(app)
+
+        formatter = logging.Formatter(fmt)
+        stream = ListStream()
+
+        handler = TestingStreamHandler(stream=stream)
+        handler.setLevel(logging.DEBUG)
+        handler.setFormatter(formatter)
+
+        app.logger.addHandler(handler)
+        app.logger.setLevel(logging.DEBUG)
+
+        return app, stream
+
+    def test_keywords(self):
+        # Register our logger class as the default
+        old_logger_class = flask_logging_extras.register_logger_class()
+
+        app, log_stream = self._create_app_with_logger('%(message)s')
+
+        app.logger.info('message')
+        # With the current formatter, the last log line must be a just the
+        # message
+        self.assertEqual(log_stream.lines[-1], 'message\n')
+
+        app, log_stream = self._create_app_with_logger(
+            '%(message)s %(extra_keyword)s')
+
+        # If we don’t register 'extra_keyword' in the app config, we get a
+        # KeyError.  We set logging.raiseExceptions to False here; the
+        # reason is that this doesn’t mean an actual exception is raised,
+        # but our TestingStreamHandler does that for us (which we need for
+        # testing purposes)
+        old_raiseExceptions = logging.raiseExceptions
+        logging.raiseExceptions = False
+        with self.assertRaises(KeyError):
+            app.logger.info('message')
+        logging.raiseExceptions = old_raiseExceptions
+
+        app, log_stream = self._create_app_with_logger(
+            '%(message)s [%(extra_keyword)s]',
+            keywords={'extra_keyword': '<unset>'})
+
+        app.logger.info('message', extra_keyword='test')
+        self.assertEqual('message [test]\n', log_stream.lines[-1])
+
+        # If we don’t provide a value for a registered extra keyword, the
+        # string "<unset>" will be assigned.
+        app.logger.info('message')
+        self.assertEqual('message [<unset>]\n', log_stream.lines[-1])