def test_constructorSetsExtraChain(self):
        """
        Setting C{extraCertChain} works if C{certificate} and C{privateKey} are
        set along with it.
        """
        opts = sslverify.OpenSSLCertificateOptions(
            privateKey=self.sKey,
            certificate=self.sCert,
            extraCertChain=self.extraCertChain,
        )
        self.assertEqual(self.extraCertChain, opts.extraCertChain)

        Setting C{extraCertChain} works if C{certificate} and C{privateKey} are
        set along with it.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_sslverify.py