In addition to Microsoft-provided apps, you can use partner apps. Microsoft rigorously validates the functionality and security of all of these apps. Elaborate manual and automated tests are executed before making these apps available in Teams store, and many tests continue at a regular cadence even after an app is published live. To understand the benefits of app validation, see validation of partner apps. Some of the apps subscribe to the Microsoft compliance program to undergo multiple tiers of further checks beyond validation. See an Overview of partner apps.