'Any warnings emitted after a call to C{flushWarnings} can be flushed by
another call to C{flushWarnings}.'

def test_multipleFlushes(self):

    warnings.warn('first    message')
    self.assertEqual(len(self.flushWarnings()), 1)
    warnings.warn('second    message')
    self.assertEqual(len(self.flushWarnings()), 1)
