PegaUnit is the new test automation framework introduced for unit testing of rules. From 7.2.2 onwards there is support for testing activity rules using it. In 7.2.1, as invocation of form based rules is deprecated, you are not able to create or edit the AUT for activity properly. We suggest you to not use the old AUT framework for creation of test cases and would suggest you to take up automation using Pega Unit framework. In 7.2.1, Data pages can be tested using it. Help documentation and PDN should be able to provide more information. From 7.2.2 onwards there is support for unit testing more rule types using it.