def test_fileDescriptorOverrun(self):
        """
        If L{IUNIXTransport.sendFileDescriptor} is used to queue a greater
        number of file descriptors than the number of bytes sent using
        L{ITransport.write}, the connection is closed and the protocol connected
        to the transport has its C{connectionLost} method called with a failure
        wrapping L{FileDescriptorOverrun}.
        """
        cargo = socket()
        server = SendFileDescriptor(cargo.fileno(), None)

        client = ReceiveFileDescriptor()
        result = []
        d = client.waitForDescriptor()
        d.addBoth(result.append)
        d.addBoth(lambda ignored: server.transport.loseConnection())

        runProtocolsWithReactor(self, server, client, self.endpoints)

        self.assertIsInstance(result[0], Failure)
        result[0].trap(ConnectionClosed)
        self.assertIsInstance(server.reason.value, FileDescriptorOverrun)

        If L{IUNIXTransport.sendFileDescriptor} is used to queue a greater
        number of file descriptors than the number of bytes sent using
        L{ITransport.write}, the connection is closed and the protocol connected
        to the transport has its C{connectionLost} method called with a failure
        wrapping L{FileDescriptorOverrun}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_unix.py