If you need to move data center, and want to be able to test everything prior to the move, using fake DNS can help.
You can set up a temporary DNS server, and configure your desktops / laptops (those that will be used for testing) to use this temporary DNS server.
Depending on our scenario, we may be able to modify the host file on these work stations instead of modifying the DNS server. (I am not sure if the host file can handle wild card).
After all the testing is done, we can reconfigure these work stations back to their normal settings, and take down our temporary DNS server.