
using Xunit;
using System;
using System.IO;

namespace ConsoleApp {
    public class ProgramTests {
        [Fact(DisplayName = "PrintCountdown prints numbers from 10 to 0 on separate lines in descending order")]
        public void PrintCountdown_PrintsCountdownCorrectly()
        {
            var sw = new StringWriter();
            Console.SetOut(sw);

            Program.PrintCountdown();

            string output = sw.ToString().Trim();
            string[] lines = output.Split(new[] { '\\n', '\\r' }, StringSplitOptions.RemoveEmptyEntries);
            int[] expected = new int[11];
            for (int i = 0; i <= 10; i++)
                expected[i] = 10 - i;
            Assert.Equal(11, lines.Length);
            for (int i = 0; i < 11; i++)
            {
                Assert.True(int.TryParse(lines[i], out int val), $"Line {i + 1} is not a valid integer");
                Assert.Equal(expected[i], val);
            }
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }
    }
}

ProgramTests.cs

Deepen your understanding of C# loops with a hands-on, challenge-driven course. Explore for, while, and do-while loops, master nested structures, generate patterns, and tackle real-world problems. Each section alternates between engaging theory and practical coding challenges to ensure you build both conceptual understanding and practical fluency.

Challenge: Countdown Timer

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