public void Single_With_Multiple_Must_Return_None(int[] source)
        {
            // Arrange
            var wrapped = Wrap
                          .AsValueReadOnlyCollection(source);

            // Act
            var result = ValueReadOnlyCollectionExtensions
                         .Single <Wrap.ValueReadOnlyCollectionWrapper <int>, Wrap.Enumerator <int>, int>(wrapped);

            // Assert
            _ = result.Must()
                .BeOfType <Option <int> >()
                .EvaluateTrue(option => option.IsNone);
        }
        public void Single_With_Single_Must_Return_Some(int[] source)
        {
            // Arrange
            var wrapped = Wrap
                          .AsValueReadOnlyCollection(source);
            var expected = Enumerable
                           .Single(source);

            // Act
            var result = ValueReadOnlyCollectionExtensions
                         .Single <Wrap.ValueReadOnlyCollectionWrapper <int>, Wrap.Enumerator <int>, int>(wrapped);

            // Assert
            _ = result.Match(
                value => value.Must().BeEqualTo(expected),
                () => throw new Exception());
        }