Each merchant account has three different process modes. These process modes are Live, Test and Demo. When using IATS, the Test process mode may not be an option within the merchant account setup.
This occurs when the security certificate has expired for Test BBPS. This certificate can be renewed by browsing to https://10.32.1.10. On this page, you should get a security certificate error message. You can click to view the certificate information and the install the new certificate. Once completed, the Test Process Mode should be available in the merchant account.