'Remove all secure sources and assert it raises a failure. Then try the
fallback parameter.'

def test_withoutAnything(self):

    self.factory._osUrandom = self.errorFactory
    self.assertRaises(randbytes.SecureRandomNotAvailable, self.factory.secureRandom, 18)
    def wrapper():
        return self.factory.secureRandom(18, fallback=True)
    s = self.assertWarns(RuntimeWarning, 'urandom    unavailable    -    proceeding    with    non-cryptographically    secure    random    source', __file__, wrapper)
    self.assertEqual(len(s), 18)
