To determine which features changed, you would check the Release Notes and Change Impact and Upgrade Guides for each release. In this case, 14.3, 14.4, 15.1, 15.2, and then 15.3. Plus any 15.3.0.x patches. All on docops.ca.com. Use the Versions menu to switch releases. Prioritize by the features you value most in your currently recognized business process and governance plans. For example, if XOG is a priority, test XOG, if Microsoft Project integration is not a high priority, move it down your list. Generally, you want to assume bugs are fixed and improvements are available, and can manage by exception; however, what often causes issues with such a leap from 14.2 to 15.3 is customization and legacy processes rooted in the past. The New User Experience in PPM offers the most value when customers can make the leap of faith to abandon old workflows and embrace new agile methodologies. Customers are telling us they can use the new features in 15.2 and higher without impediments and realize immediate value. In other words, you might find that core classic functionality works as expected (remove your customizations, of course) and that new ways of working replace old methods so legacy test cases would no longer apply. Wishing you every success in test and smooth migration to prod.