WPF

button.Width = 123;
Assert.AreEqual(123, button.ActualWidth);

[TestMethod()]
public void LayoutTest()
{
    // simulate user input
    ItemPeer1.Move(50, 100);

    // execute the tested method
    LayoutAlgorithm.Layout(TheScatterView); // modifies the center of some items (in this case item2 should be updated)

    // test if the layout algorithm works correctly
    Assert.AreEqual(new Point(50, 100), Item1.Center); // using ActualCenter would fail
    Assert.AreEqual(new Point(200, 100), Item2.Center); // fails.
    // ...
}

button.Width = 123;
DoSomethingSoThatActualWidthGetsUpdated(); // what to do here?
Assert.AreEqual(123, button.ActualWidth);

<Window x:Class="TestShrinkListView.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <Border BorderThickness="2" BorderBrush="Red" VerticalAlignment="Top">
        <ListView Height="Auto" VerticalAlignment="Top">
            <ListViewItem>
                <TextBox AcceptsReturn="True">Type some text here.</TextBox>
            </ListViewItem>
        </ListView>
    </Border>
</Window>