import os
import sys
import unittest
import warnings

sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)),
                                '../src'))

class CatchWarningsMixin(object):
    class assertWarns(object):
        def __init__(self, warningtype, msg=''):
            self.warningtype = warningtype
            warnings.filterwarnings('error')
            self.failureException = unittest.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