I have any information about Impact Analysis for you.
If any change code, or implement new function on the old system, we need to do impact analysis document.
+ It need the Dev's help, help us list all relating code files, relating URL files, all new files or new function will be added, all information relating to these changes....
+ After that, we list all test-cases relate to all information as was listed above by Dev. At this steps, maybe we must to update test-cases or write new test-cases to can cover all these changes.