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Mocking logging module for unittests

under Python, Logging, Mock, English

Today I was writing tests for upcoming application I'm writing (more information will come later) and I needed some way to redirect logging to some kind of storage that could be easily asserted to values in tests. First I tried with monkey patching it, but that wasn't the solution since all logging setup is done before pylons tests come to play, so somebody in IRC pointed me toward writing a handler. I thought to do so in the first place, but were too stubborn;)

Here is the handler code:

class ListHandler(logging.Handler):

    debug = []
    warning = []
    info = []
    error = []

    def emit(self, record):
        getattr(self.__class__, record.levelname.lower()).append(record.getMessage())

    def reset(cls):
        for attr in dir(cls):
            if isinstance(getattr(cls, attr), list):
                setattr(cls, attr, [])

So basically, all records are stored in handlers class(!), which is restored to zero on every tearDown() call. Later in the code, I can do stuff like:

def test_foobar(self):
        self.failUnless('Invalid status' in  ListHandler.warning)