public void ValueDisplayValue_ChangeFromValidToInvalidValue_SetsDisplayValueToInvlaidValueAndValueRemainsUnChanged()
{
var vm = new TestVM();
decimal?validValue = 1;
vm.SetValue(x => x.Value, validValue);
Assert.AreEqual(validValue, vm.GetValidatedValue());
Assert.AreEqual(validValue, vm.GetDisplayValue());
decimal?invalidValue = 2;
vm.InvalidateValue = true;
vm.SetDisplayValue(invalidValue);
Assert.AreEqual(validValue, vm.GetValidatedValue());
Assert.AreEqual(invalidValue, vm.GetDisplayValue());
}