
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

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Challenge: Reverse Playlist

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