
using Xunit;
namespace ConsoleApp {
    public class ProgramTests {
        [Fact(DisplayName = "ReversePlaylist reverses even-length array in place")]
        public void ReversePlaylist_EvenLengthArray_ReversesInPlace()
        {
            string[] playlist = { "Song A", "Song B", "Song C", "Song D" };
            Program.ReversePlaylist(playlist);
            Assert.Equal(new[] { "Song D", "Song C", "Song B", "Song A" }, playlist);
        }

        [Fact(DisplayName = "ReversePlaylist reverses odd-length array in place")]
        public void ReversePlaylist_OddLengthArray_ReversesInPlace()
        {
            string[] playlist = { "One", "Two", "Three" };
            Program.ReversePlaylist(playlist);
            Assert.Equal(new[] { "Three", "Two", "One" }, playlist);
        }

        [Fact(DisplayName = "ReversePlaylist reverses single-element array correctly")]
        public void ReversePlaylist_SingleElement_NoChange()
        {
            string[] playlist = { "Solo" };
            Program.ReversePlaylist(playlist);
            Assert.Equal(new[] { "Solo" }, playlist);
        }

        [Fact(DisplayName = "ReversePlaylist reverses empty array with no error")]
        public void ReversePlaylist_EmptyArray_NoError()
        {
            string[] playlist = { };
            Program.ReversePlaylist(playlist);
            Assert.Empty(playlist);
        }

        [Fact(DisplayName = "ReversePlaylist modifies the original array, not a copy")]
        public void ReversePlaylist_ModifiesOriginalArray()
        {
            string[] playlist = { "A", "B", "C" };
            string[] reference = playlist;
            Program.ReversePlaylist(playlist);
            Assert.Same(reference, playlist);
        }
    }
}

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.

Challenge: Reverse Playlist

Solution