You have provided no information about:
- from & to platforms
- whether the AUT platform and/or the test platform is changing
- whether your question relates to test inputs and/or AUT output...
If your tests are structured correctly and/or your test bed is adequate, all points should be a non-issue.
If field definitions are changing as a result of the platform migration, then your main focus should be boundary & partition equivalence on your existing data and/or changes to the field boundaries of existing variables on the new platform...