Three areas that should be tested as part of data migration are: data transformation against source system, contact association with correct account, and account and lead ownership. These areas can help ensure that the data is migrated correctly and accurately, and that the relationships and ownership are preserved. Lead assignment is not an area that should be tested as part of data migration, as it is a business process that is triggered after the data is migrated. Page layout assignments is also not an area that should be tested as part of data migration, as it is a configuration setting that is independent of the data. See Data Migration for more details.