Any changes you make to your app risks breaking existing functionality. Having a suite of automated tests that you can run prior to any release reduces the risk of releasing a product with new features that don't work, or that breaks existing features. It also means that you can run these tests as part of your CI/CD pipeline.
Every control in .NET MAUI exposes the AutomationId property, which allows a UI testing framework to find and interact with contols. This article demonstrates how you can write and run your UI tests with Appium.
Unlike Xamarin, .NET MAUI doesn't come with a built-in UI testing framework - Xamarin.UITest. Technically, you still can use Xamarin.UITest with .NET MAUI, but only to unblock your team to migrate from Xamarin. For details, see this video by Gerald Versluis.
