public async Task StartTracking_Should_start_listening_for_changes() { _permissionValidator.ValidateGeolocationPermission().Returns(true); _geolocator.IsListening.Returns(false); await _trackerService.StartTracking(); await _geolocator.Received(1).StartListeningAsync(Arg.Any <TimeSpan>(), Arg.Any <double>()); _geolocator.Received(1).PositionChanged += Arg.Any <EventHandler <PositionEventArgs> >(); }