def test_constructor(self):
        """
        Stores an L{IProtocol} provider and the flag to log/drop stderr
        """
        d = self.ep.connect(self.factory)
        self.successResultOf(d)
        wpp = self.reactor.processProtocol
        self.assertIsInstance(wpp.protocol, StubApplicationProtocol)
        self.assertEqual(wpp.errFlag, self.ep._errFlag)

        Stores an L{IProtocol} provider and the flag to log/drop stderr
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_endpoints.py