AD Upgrade

Dears,

I have deployed my new DCs in all of my sites, then I have done with below:

1. Moved FSMO roles to new DCs
2. Configured bridgehead servers
3. Remove check box of GC from my old DCs
4. Make sure that my new DCs are GCs
5. I configure all my DCs, Servers, and Clients TCP/IP DNS settings to use my new DCs
6. My DCs does not include encrypted data

Now I need to test my environment for 10 days, while my old DCs are shutdown.

I shutdown my old DCs, I run the command: "dcdiag /test:dns" and it fail.

So how should I test my environment while my old DCs are shutdown?