public void IsVisibleTest()
{
// Arrange.
var rootVisual = new StackPanel { Visibility = Visibility.Visible };
var visibleContainer = new StackPanel { Visibility = Visibility.Visible };
rootVisual.Children.Add(visibleContainer);
var collapsedContainer = new StackPanel { Visibility = Visibility.Collapsed };
rootVisual.Children.Add(collapsedContainer);
var textBoxInVisibleContainer = new TextBox { Visibility = Visibility.Visible };
visibleContainer.Children.Add(textBoxInVisibleContainer);
var textBoxInCollapsedContainer = new TextBox { Visibility = Visibility.Visible };
collapsedContainer.Children.Add(textBoxInCollapsedContainer);
var textBoxNotInVisualTree = new TextBox { Visibility = Visibility.Visible };
Mock.Arrange(() => Application.Current.RootVisual).Returns(rootVisual);
// Act / Assert.
Assert.IsTrue(rootVisual.IsVisibile());
Assert.IsTrue(visibleContainer.IsVisibile());
Assert.IsFalse(collapsedContainer.IsVisibile());
Assert.IsTrue(textBoxInVisibleContainer.IsVisibile());
Assert.IsFalse(textBoxInCollapsedContainer.IsVisibile());
Assert.IsFalse(textBoxNotInVisualTree.IsVisibile());
}