def test_getReturnsNewIfCacheEmpty(self):
        """
        If there are no cached connections,
        L{HTTPConnectionPool.getConnection} returns a new connection.
        """
        self.assertEqual(self.pool._connections, {})

        def gotConnection(conn):
            self.assertIsInstance(conn, StubHTTPProtocol)
            # The new connection is not stored in the pool:
            self.assertNotIn(conn, self.pool._connections.values())

        unknownKey = 12245
        d = self.pool.getConnection(unknownKey, DummyEndpoint())
        return d.addCallback(gotConnection)

        If there are no cached connections,
        L{HTTPConnectionPool.getConnection} returns a new connection.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_agent.py