“An unidentifed error has occurred"
means that there is a problem with the Site Definition settings for connecting to the Testing server.
If you are trying to connect to the remote database, set up the testing server settings in your site definition to use FTP and use the credential for connecting to the remote server.
if the FTP server connects bellow the site root, make sure to add the Host Directory so that it connects to the root.
also make sure that the URL prefix is the correct address to point to the same location as the FTP Settings.