You may face issue while configuring TFS 2010 with the test controller which is in different domain.
If you want to register a test controller that is in a workgroup or a different domain that does not have a two-way trust with the domain for your Team Foundation Server, you must also create a local user account with the same user name and password on the Team Foundation Server machine and the test controller machine. This local user account must also be added as a member of the following Team Foundation Server group: [Project Collection]\Project Collection Test Service Accounts. Then you can register the test controller using this local user account when you run the test controller configuration tool.
In case this fails, these are possible checks:
(a) In case you still face the issue, login with the account which you are using to configure test controller.
(b) Add the DNS entry for the controller in the TFS AT host file and vice versa.
Content developed by: Deepak Mittal
Content reviewed by: Teodora Stanev