How to create unit test for ActualWidth in Silverlight 4?

How can I write a 开发者_开发问答unit test to test the ActualWidth property in a UserControl in Silverligh 4?

I hoped that this method would pass, but it fails.

I am using the Silverlight ToolKit april 2010, and VS 2010.

<TestMethod()> _
Public Sub TestAcrtualWidth()
    Me.MyUserControl.Width = 100
    Me.MyUserControl.UpdateLayout()
    Assert.IsTrue(Me.MyUserControl.ActualWidth > 0)
End Sub

The problem was that I added MyUserControl to a new instance of a Canvas. If I instead used :

Me.TestPanel.Children.add(Me.MyUserControl) 

It worked!