How do you mock platform/device services for testing?

Abstract device features behind interfaces (e.g., IGeolocation, IConnectivity—MAUI already provides interfaces for many Essentials APIs) and inject them. In tests supply fakes/mocks. Avoid calling static Essentials members directly in logic; depend on the interface so tests don't touch real hardware.

// Production: inject IConnectivity; Test: pass a stub
public SyncViewModel(IConnectivity connectivity) => _c = connectivity;

var vm = new SyncViewModel(new StubConnectivity(NetworkAccess.None));