Migrating SQL server, concern about servername

Question

I'm getting ready to migrate from SQL Server 2005 onto a new server with SQL Server 2012, and a question was brought up this morning (and the migration is tomorrow of course).
The old server was called XYZ and the DB had the same name. So, in connection strings we were just using XYZ to connect.
On the new server, I also named the DB XYZ, but to connect I use NewServer/XYZ.
The plan is that tmrw when we go live with the new DB to rename the server XYZ and give it the old servers IP address so that everything that connects to it will run, business as usual.
The concern from one of the sysops is that once we change the servername we'll need to use XYZ/XYZ to connect to the new server.
I was hoping that someone could point me towards how to test for this before going live? Having to change all the connections would be a big job and include a lot of downtime.

Answer 1

You can't change the instance name (the bit after the \\ ). So you'll need to connect using XYZ\\XYZ.