
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.

Explore the full power of for loops in C#, from basic counting to custom steps and real-world data processing.

Master while and do-while loops for scenarios where the number of iterations isn't known in advance, and learn to control loop execution with conditions.

Delve into advanced looping techniques, including nested loops for pattern generation, loop transformations, efficiency, and avoiding common mistakes.

Challenge: Filter Even Numbers

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