I called the OnMap method but it's giving me the error message that I did not use it.

namespace TreehouseDefense
{
    public class Map
    {
        public readonly int Width;
        public readonly int Height;

        public Map(int width, int height)
        {
            if(width < 1 || height < 1)
            {
                throw new System.ArgumentOutOfRangeException(
                    "Map must be at least 1x1");
            }

            Width = width;
            Height = height;
        }

        public bool OnMap(Point point)
        {
            return point.X >= 0 && point.X < Width && 
                   point.Y >= 0 && point.Y < Height;
        }
    }
}

using Xunit;

namespace TreehouseDefense.Tests
{
    public class MapTests
    {
        [Fact]
        public void OnMapTest()
        {

            int x = 2;
            int y = 4;
            int Width =x;
            int Length = y;

            var point = new Point (x, y);
            var OnMap = new OnMap(Width, Length);

            Assert.Equals(Width, OnMap.Width);
            Assert.Equals(Length, OnMap.Length);
        }
    }
}

using System;

namespace TreehouseDefense
{
    public class Point
    {
        public readonly int X;
        public readonly int Y;

        public Point(int x, int y)
        {
            X = x;
            Y = y;
        }

        public double DistanceTo(Point point)
        {
            return Math.Sqrt(Math.Pow(X - point.X, 2.0) + Math.Pow(Y - point.Y, 2.0));
        }
    }
}