public void EnumRemoveExtension()
{
Fruits basket = Fruits.Banana;
basket = basket.Add(Fruits.Pineapple);
basket = basket.Remove(Fruits.Banana);
Assert.False(basket.Contains(Fruits.Banana));
Assert.True(basket.Contains(Fruits.Pineapple));
Assert.False(basket.Contains(Fruits.Durian));
}