Пунктуация

namespace Human_readable_duration_format
{
    public class HumanTimeFormat
    {
        public static string formatDuration(int seconds)
        {
            if (seconds == 0) return "now";
            if (seconds < 60 && seconds>1) return $"{seconds} seconds";
            if (seconds == 1) return $"{seconds} second";
 
            int min = seconds / 60;
            seconds = seconds % 60;
            int hours = min / 60;
            min = min % 60;
            int days = hours / 24;
            hours = hours % 24;
            int years = days / 365;
            days = days % 365;
 
            string _years, _days, _hour, _minute, _second;
            
            _years=S(years, "year");
            _days = S(days, "day");
            _hour = S(hours, "hour");
            _minute = S(min, "minute");
            _second = S(seconds, "second");            
 
            string result = _years +_days +_hour + _minute + _second;
 
            
 
            return result;
            
        }
 
 
        public static string S (int value, string param)
        {
            string result;
 
            if (value > 1) result = $"{value} {param}s";
            else if (value == 1) result = $"{value} {param}";
            else result = "";
            
            return result;
        }
   }
}

using NUnit.Framework;
using System;
 
using Human_readable_duration_format;
 
namespace HumanTimeFormatTest
{
    [TestFixture]
    public class Tests
    {
        [Test]
        public void basicTests()
        {
            Assert.AreEqual("now", HumanTimeFormat.formatDuration(0));
            Assert.AreEqual("1 second", HumanTimeFormat.formatDuration(1));
            Assert.AreEqual("1 minute and 2 seconds", HumanTimeFormat.formatDuration(62));
            Assert.AreEqual("2 minutes", HumanTimeFormat.formatDuration(120));
            Assert.AreEqual("1 hour, 1 minute and 2 seconds", HumanTimeFormat.formatDuration(3662));
            Assert.AreEqual("182 days, 1 hour, 44 minutes and 40 seconds", HumanTimeFormat.formatDuration(15731080));
            Assert.AreEqual("4 years, 68 days, 3 hours and 4 minutes", HumanTimeFormat.formatDuration(132030240));
            Assert.AreEqual("6 years, 192 days, 13 hours, 3 minutes and 54 seconds", HumanTimeFormat.formatDuration(205851834));
            Assert.AreEqual("8 years, 12 days, 13 hours, 41 minutes and 1 second", HumanTimeFormat.formatDuration(253374061));
            Assert.AreEqual("7 years, 246 days, 15 hours, 32 minutes and 54 seconds", HumanTimeFormat.formatDuration(242062374));
            Assert.AreEqual("3 years, 85 days, 1 hour, 9 minutes and 26 seconds", HumanTimeFormat.formatDuration(101956166));
            Assert.AreEqual("1 year, 19 days, 18 hours, 19 minutes and 46 seconds", HumanTimeFormat.formatDuration(33243586));
        }
    }
}