import asyncio
from test.test_asyncio import utils as tu

class Proto(asyncio.Protocol):
    def connection_made(self, tr):
        self.tr = tr
    def connection_lost(self, exc):
        self.tr.close()
        self.lost.set_result(None)

async def main():
    async def handler(reader, writer):
        writer.close()
    srv = await asyncio.start_server(handler, '127.0.0.1', 0,
                                     ssl=tu.simple_server_sslcontext())
    port = srv.sockets[0].getsockname()[1]
    loop = asyncio.get_running_loop()
    proto = Proto()
    proto.lost = loop.create_future()
    tr, _ = await loop.create_connection(
        lambda: proto, '127.0.0.1', port, ssl=tu.simple_client_sslcontext())
    await proto.lost
    tr.write(b'x')  # AttributeError: 'NoneType' object has no attribute '_write_appdata'
    srv.close()

asyncio.run(main())