I'm creating an Email Delivery and to personalise content I'm using attributes from custom resources (using "Add data" tab in the Query). This is working fine however because the Test Profiles are not linked to any custom resources it is not possible to preview content with personalisation fields populated as well as send test message to test the personalisation fields and dynamic elements. I know that it's possible to preview the content for each recipient after the "prepare delivery" process however there should be a way to test the content before that?
With respect to ACS, currently there is no substitution address you can give to test the delivery content, when you have level of personalization generated from custom resources. Workaround is you can have mock profiles and also you will have to differentiate mock vs real profile. Then populate sample data using the mock profile and try to segment the mock profile as one-off email delivery to test content before you send to target audience. Incase, if you're having different variant to the personalized data then you need to setup some process to setup additional mock profiles and populate the fields using data import.