public void LazyLessThanShouldThrowIfValueProviderIsNull()
        {
            Action action = () => Pattern.LessThan((Func <int>)null);

            action.Should().Throw <ArgumentNullException>();
        }
 public Property LazyLessThanShouldSucceedOnlyWhenValueIsLess(string x, string y)
 => (Comparer <string> .Default.Compare(x, y) < 0 == Pattern.LessThan(() => y).Match(x).IsSome).ToProperty();