private void TryToTimeSpanFriendly(TimeSpan?expected, string value)
        {
            String8 value8 = value.TestConvert();

            TimeSpan actual;
            bool     succeeded = value8.TryToTimeSpanFriendly(out actual);

            Assert.AreEqual(expected.HasValue, succeeded, $"Success wrong for '{value}'");
            Assert.AreEqual(expected ?? TimeSpan.Zero, actual, $"Result wrong for '{value}'");
        }