public void PropertyChancedCallbackIsCalled()
        {
            var objectUnderTest = new FirstDependencyObject();
            Assert.Equal(
                FirstDependencyObject.DefaultTestValue,
                objectUnderTest.Test);

            objectUnderTest.Test = 42;
            Assert.Equal(
                42,
                objectUnderTest.Test);
            Assert.Equal(
                FirstDependencyObject.DefaultTestValue,
                objectUnderTest.LastValue);
        }
 private static void Callback(FirstDependencyObject d, DependencyPropertyChangedEventArgs<int> e)
 {
     d.LastValue = e.OldValue;
 }