Unit testing is a vast and complex area. Flask has some excellent documentation on other techniques for writing effective tests: http://flask.pocoo.org/docs/0.10/testing/.

Python, of course, has its own documentation on unit testing: https://docs.python.org/2/library/unittest.html.

Flask uses the logging module from Python for its logging. This, in turn, follows the C library structure for its logging levels. More detail can be found at: https://docs.python.org/2/library/logging.html.