When we going to upgrade the system SAP will give us instruction manual which gives us the information where exactly changes have taken place, this can be collected from Basis team accordingly we can plan our testing process apart from this we have to check day to day transactions which we are using regularly so that we can come to any inconsistencies are there same can be communicated to SAP team else we can resolve on our own with considering our team members i.e technical, basis, customer.
Get in touch with Basis team to get manual.
Regards
Venkatesh