onlostfocus

[WPF] How can I force a textBox in wpf to call OnLostFocus in a unit test?

I have a custom component created in WPF using C#, where I have some validation that are checked when the textbox OnLostFocus is called (it is only when the user leaves the textbox I can do the validation, since only then do I have the complete input string to validate). How can I trigger the OnLostFocus on the textBox from the unit tes...