Did a lot of work just unit testing left

Shapes/CompositeShape.cs

@@ -0,0 +1,87 @@
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.IO;
+using System.Linq;
+
+namespace Shapes
+{
+    public class CompositeShape : Shape
+    {
+        private List<Shape> thisShapesList = new List<Shape>();
+        
+        public override Color Fill { get; set; }
+        public override Color Stroke { get; set; }
+
+        public void Add(Shape shape)
+        {
+            if(shape.CompositeShape)
+                throw new ShapeException($"This shape has already been added to a composite");
+            if(shape == this)
+                throw new ShapeException($"You cant add a shape to itself");
+            thisShapesList.Add(shape);
+            shape.CompositeShape = true;
+        }
+
+        
+
+        public override double ComputeArea()
+        {
+            return thisShapesList.Sum(d => d.ComputeArea());
+        }
+
+        public override void Scale(double scaleFactor)
+        {
+            foreach (var shape in thisShapesList)
+            {
+                shape.Scale(scaleFactor);
+            }
+        }
+
+        public override void Save(Stream stream)
+        {
+            var fileWriter = new FileIO();
+            fileWriter.SaveShape(stream, this); 
+        }
+
+        public override void Draw(Stream stream)
+        {
+            var tmp = new Bitmap(1000, 1000);
+            Pen blackPen = new Pen(Stroke, 3);
+            // Draw line to screen.
+            using (var graphics = Graphics.FromImage(tmp))
+            {
+                foreach (var shape in thisShapesList)
+                {
+                    for (int i = 1; i < shape.Points.Count; i++)
+                        graphics.DrawLine(blackPen, (float) shape.Points[i - 1].X, (float) shape.Points[i - 1].Y, (float) shape.Points[i].X,
+                            (float) shape.Points[i].Y);
+                }
+                
+            }
+
+            tmp.Save(stream, ImageFormat.Jpeg);
+        }
+
+
+        public void RemoveShape(Shape shape)
+        {
+            if(!thisShapesList.Contains(shape))
+                throw new ShapeException($"{shape.GetType().Name} is not part of the composite shape.");
+            thisShapesList.Remove(shape);
+            shape.CompositeShape = false;
+            
+        }
+
+        public void RemoveAllShapes()
+        {
+            while (thisShapesList.Count > 0)
+            {
+                thisShapesList[0].CompositeShape = false;
+                thisShapesList.Remove(thisShapesList[0]);
+            }
+        }
+
+    }
+}