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

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