import warnings

__unittest=True

class _AssertWarnsContext(object):

    def __init__(self, warningtype, testcase, msg=''):

        self.warningtype = warningtype

        warnings.filterwarnings('error')

        self.failureException = testcase.failureException

    def __enter__(self):

        return self

    def __exit__(self, exc_type, exc_value, tb):

        if exc_type is None:

            try:

                exc_name = self.warningtype.__name__

            except AttributeError:

                exc_name = str(self.warningtype)

            raise self.failureException(

                "{0} not raised".format(exc_name))

        if not issubclass(exc_type, self.warningtype):

            raise self.failureException('"%s" does not match "%s"' %

                    (self.warningtype.__name__, str(exc_type.__name__)))

        return True

class CatchWarningsMixin(object):

    def assertWarns(self, wrnClass, callableObj=None, *args, **kwargs):

        context = _AssertWarnsContext(wrnClass, self)

        if callableObj is None:

            return context

        with context:

            callableObj(*args, **kwargs)