write unit test case for collaborationplatform beginstartup()

hi

how to write  unit test case for collaborationplatform beginstartup?

 var platformSettings = new ClientPlatformSettings(userAgent, Microsoft.Rtc.Signaling.SipTransportType.Tls);
            _collabPlatform = new CollaborationPlatform(platformSettings);

            //Start up the platform, calling back asynchronously once it's done.
            _collabPlatform.BeginStartup(EndCollabPlatformStartup, null);

private static void EndCollabPlatformStartup(IAsyncResult ar)
        {
            _collabPlatform.EndStartup(ar);

            //A collaboration plaform can have one or more Endpoints. An Endpoint is tied to a SIP Address.            
            UserEndpointSettings settings = new UserEndpointSettings(sipaddress);
            settings.Credential = new System.Net.NetworkCredential(username, password, domain);
            settings.AutomaticPresencePublicationEnabled = true;

            _endpoint = new UserEndpoint(_collabPlatform, settings);
            _endpoint.BeginEstablish(UserEndpointEstablishCompleted, null);

        }