How to validate Call button in Xamrin UI test?

I have Call Us button in my android application.

Functionality: I click on Call Us button, the application goes to background and phones dialer pops up with the phone number prefilled.

How to validate it in Xamarin UI test case. I am new to writing test cases please help thanks. However in iOS, it prompts alert on which I can validate but in android, it directly opens up the dialer.