
using Xunit;
using System;
using System.IO;

namespace ConsoleApp {
    public class ProgramTests {
        [Fact(DisplayName = "PrintOddNumbersWhile skips even numbers and prints odd numbers only")] 
        public void PrintOddNumbersWhile_PrintsOnlyOddNumbers() {
            var sw = new StringWriter();
            Console.SetOut(sw);
            int[] arr = { 8, 13, 20, 25, 34, 41, 56, 67 };
            Program.PrintOddNumbersWhile(arr);
            string output = sw.ToString().Trim();
            Assert.Contains("13", output);
            Assert.Contains("25", output);
            Assert.Contains("41", output);
            Assert.Contains("67", output);
            Assert.DoesNotContain("8", output);
            Assert.DoesNotContain("20", output);
            Assert.DoesNotContain("34", output);
            Assert.DoesNotContain("56", output);
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }

        [Fact(DisplayName = "PrintOddNumbersWhile prints nothing for all even numbers array")]
        public void PrintOddNumbersWhile_AllEvenNumbers_PrintsNothing() {
            var sw = new StringWriter();
            Console.SetOut(sw);
            int[] arr = { 2, 4, 6, 8, 10 };
            Program.PrintOddNumbersWhile(arr);
            string output = sw.ToString().Trim();
            Assert.True(string.IsNullOrEmpty(output), "Expected no output for all even numbers array");
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }

        [Fact(DisplayName = "PrintOddNumbersWhile prints all numbers for all odd numbers array")]
        public void PrintOddNumbersWhile_AllOddNumbers_PrintsAll() {
            var sw = new StringWriter();
            Console.SetOut(sw);
            int[] arr = { 1, 3, 5, 7 };
            Program.PrintOddNumbersWhile(arr);
            string output = sw.ToString().Trim();
            Assert.Contains("1", output);
            Assert.Contains("3", output);
            Assert.Contains("5", output);
            Assert.Contains("7", output);
            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: Filter Even Numbers

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