'Once C{runWithWarningsSuppressed} has returned, it no longer
suppresses warnings.'

def test_noSideEffects(self):

    filters = [(('ignore', '.*foo.*'), {}), (('ignore', '.*bar.*'), {})]
    self.runWithWarningsSuppressed(filters, (lambda : None))
    warnings.warn('ignore    foo')
    self.assertEqual(['ignore    foo'], [w['message'] for w in self.flushWarnings()])
