Summary
RSAT is a useful tool if you want to validate business scenarios and do automated testing before deployment to production, especially when you have completed a system customization and new features exist.
Before deploying the extension package to production, test cases should be run to ensure that everything is validated and that all business processes can be run through.
Test cases in Azure DevOps are updated with the result of the testing. RSAT can analyze and check any errors that might have occurred. These errors can be checked in Azure DevOps, which will also show the reason behind the test fail in the history display of the exception log.