public void When_Placement_Full() { var SUT = new Grid() { Name = "test" }; var flyout = new Flyout() { Placement = Windows.UI.Xaml.Controls.Primitives.FlyoutPlacementMode.Full, FlyoutPresenterStyle = new Style { Setters = { new Setter(FrameworkElement.MaxWidthProperty, double.PositiveInfinity), new Setter(FrameworkElement.MaxHeightProperty, double.PositiveInfinity) } } }; var button = new Button() { Flyout = flyout }; //button.Click; flyout.ShowAt(button); var presenter = flyout.GetPresenter(); var panel = flyout.GetPopupPanel(); var visibleBounds = new Rect(0, 0, 410, 815); var applicationView = ApplicationView.GetForCurrentView(); using (applicationView.SetVisibleBounds(visibleBounds)) { panel.Measure(visibleBounds.Size); panel.Arrange(visibleBounds); Assert.AreEqual(410d, presenter.ActualWidth); Assert.AreEqual(815d, presenter.ActualHeight); } }