public async Task ValidateOverlayBrush() { TestCleanupWrapper cleanup; CalendarDatePicker calendarDatePicker = null; await RunOnUIThread(() => { calendarDatePicker = new CalendarDatePicker(); calendarDatePicker.LightDismissOverlayMode = LightDismissOverlayMode.On; TestServices.WindowHelper.WindowContent = calendarDatePicker; }); await TestServices.WindowHelper.WaitForIdle(); TestServices.InputHelper.Tap(calendarDatePicker); await TestServices.WindowHelper.WaitForIdle(); FlyoutBase flyout = null; await RunOnUIThread(() => { var root = FrameworkElement(VisualTreeHelper.GetChild(calendarDatePicker, 0)); flyout = FlyoutBase.GetAttachedFlyout(root); THROW_IF_NULL_WITH_MSG(flyout, "An overlay element should exist for the flyout."); }); FlyoutHelper.ValidateOpenFlyoutOverlayBrush("CalendarDatePickerLightDismissOverlayBackground"); FlyoutHelper.HideFlyout(flyout); }