
using Xunit;
using Xunit;
using System;
using System.IO;

namespace ConsoleApp {
    public class ProgramTests {
        [Fact(DisplayName = "PrintEvenNumbers prints all and only even numbers from a mixed array")]        
        public void PrintEvenNumbers_PrintsOnlyEvenNumbers_MixedArray()
        {
            var sw = new StringWriter();
            Console.SetOut(sw);
            int[] numbers = { 1, 4, 7, 10, 13, 16, 19, 20 };
            Program.PrintEvenNumbers(numbers);
            string output = sw.ToString();
            var lines = output.Split(new[] { '\\n', '\\r' }, StringSplitOptions.RemoveEmptyEntries);
            Assert.Contains("4", lines);
            Assert.Contains("10", lines);
            Assert.Contains("16", lines);
            Assert.Contains("20", lines);
            Assert.DoesNotContain("1", lines);
            Assert.DoesNotContain("7", lines);
            Assert.DoesNotContain("13", lines);
            Assert.DoesNotContain("19", lines);
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }

        [Fact(DisplayName = "PrintEvenNumbers prints all even numbers from an all-even array")]
        public void PrintEvenNumbers_AllEvenArray()
        {
            var sw = new StringWriter();
            Console.SetOut(sw);
            int[] numbers = { 2, 4, 6, 8 };
            Program.PrintEvenNumbers(numbers);
            string output = sw.ToString();
            Assert.Contains("2", output);
            Assert.Contains("4", output);
            Assert.Contains("6", output);
            Assert.Contains("8", output);
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }

        [Fact(DisplayName = "PrintEvenNumbers prints nothing for all-odd array")]
        public void PrintEvenNumbers_AllOddArray()
        {
            var sw = new StringWriter();
            Console.SetOut(sw);
            int[] numbers = { 1, 3, 5, 7 };
            Program.PrintEvenNumbers(numbers);
            string output = sw.ToString();
            Assert.True(string.IsNullOrWhiteSpace(output), "No output should be printed for all-odd array");
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }

        [Fact(DisplayName = "PrintEvenNumbers prints nothing for empty array")]
        public void PrintEvenNumbers_EmptyArray()
        {
            var sw = new StringWriter();
            Console.SetOut(sw);
            int[] numbers = { };
            Program.PrintEvenNumbers(numbers);
            string output = sw.ToString();
            Assert.True(string.IsNullOrWhiteSpace(output), "No output should be printed for empty array");
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }
    }
}

ProgramTests.cs

Master the essentials and advanced techniques of working with arrays in C#. This course guides you from the basics of declaring and initializing arrays, through practical manipulation, searching, and advanced operations like sorting and matrix calculations. Each section blends engaging theory with real-world themed challenges to ensure a hands-on, beginner-friendly learning experience.

Start your journey with arrays in C#: learn how to declare, initialize, and access array elements, and tackle your first real-world array challenges.

Dive deeper into arrays by learning how to search for values, filter elements, and perform calculations like finding min, max, and averages.

Advance your skills by learning how to reverse arrays, sort them manually, and understand how arrays are stored and copied in memory.

Explore two-dimensional arrays, learn to perform matrix operations, and tackle real-world challenges involving grids and tables.

Challenge: Print Even Numbers

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