private const int MaxTimeout = 5 * 60 * 1000; // 5 minutes

        private SnmpEngine CreateEngine(bool timeout = false, bool max255chars = false)
        {
            // TODO: this is a hack. review it later.
            var store = new ObjectStore();

            store.Add(new SysDescr());
            store.Add(new SysObjectId());
            store.Add(new SysUpTime());
            store.Add(new SysContact());
            store.Add(new SysName());
            store.Add(new SysLocation());
            store.Add(new SysServices());
            store.Add(new SysORLastChange());
            store.Add(new SysORTable());
            store.Add(new IfNumber());
            store.Add(new IfTable());
            if (timeout)
            {
                store.Add(new TimeoutObject());
            }
            if (max255chars)
            {
                store.Add(new Max255CharsObject());
            }

            var users = new UserRegistry();

            users.Add(new OctetString("neither"), DefaultPrivacyProvider.DefaultPair);
            users.Add(new OctetString("authen"), new DefaultPrivacyProvider(new MD5AuthenticationProvider(new OctetString("authentication"))));
            if (DESPrivacyProvider.IsSupported)
            {
                users.Add(new OctetString("privacy"), new DESPrivacyProvider(new OctetString("privacyphrase"),
                                                                             new MD5AuthenticationProvider(new OctetString("authentication"))));
            }

            var getv1        = new GetV1MessageHandler();
            var getv1Mapping = new HandlerMapping("v1", "GET", getv1);

            var getv23        = new GetMessageHandler();
            var getv23Mapping = new HandlerMapping("v2,v3", "GET", getv23);

            var setv1        = new SetV1MessageHandler();
            var setv1Mapping = new HandlerMapping("v1", "SET", setv1);

            var setv23        = new SetMessageHandler();
            var setv23Mapping = new HandlerMapping("v2,v3", "SET", setv23);

            var getnextv1        = new GetNextV1MessageHandler();
            var getnextv1Mapping = new HandlerMapping("v1", "GETNEXT", getnextv1);

            var getnextv23        = new GetNextMessageHandler();
            var getnextv23Mapping = new HandlerMapping("v2,v3", "GETNEXT", getnextv23);

            var getbulk        = new GetBulkMessageHandler();
            var getbulkMapping = new HandlerMapping("v2,v3", "GETBULK", getbulk);

            var v1             = new Version1MembershipProvider(new OctetString(communityPublic), new OctetString(communityPublic));
            var v2             = new Version2MembershipProvider(new OctetString(communityPublic), new OctetString(communityPublic));
            var v3             = new Version3MembershipProvider();
            var membership     = new ComposedMembershipProvider(new IMembershipProvider[] { v1, v2, v3 });
            var handlerFactory = new MessageHandlerFactory(new[]
            {
                getv1Mapping,
                getv23Mapping,
                setv1Mapping,
                setv23Mapping,
                getnextv1Mapping,
                getnextv23Mapping,
                getbulkMapping
            });

            var pipelineFactory = new SnmpApplicationFactory(store, membership, handlerFactory);
            var listener        = new Listener {
                Users = users
            };

            listener.ExceptionRaised += (sender, e) => { Assert.True(false, "unexpected exception"); };
            return(new SnmpEngine(pipelineFactory, listener, new EngineGroup()));
        }