Regression test is key when we need to test before migration and after migration. After migration, whether the values are populated into the correct fields and validations, are matched with the data. This should not affect other fields.
This test will measure the following:
Any time requirements change (a common occurrence in Payment Solution implementations), new features are added or defects are fixed, we should run a regression test to make sure that the fixes or changes have not affected any existing functionalities.