Добавил тест для прямоугольника

StructureHelperLogics/NdmCalculations/Materials/PrimitiveMaterial.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace StructureHelperLogics.NdmCalculations.Materials
+{
+    public class PrimitiveMaterial : IPrimitiveMaterial
+    {
+        public string Id { get; }
+        public MaterialTypes MaterialType { get; set; }
+        public string ClassName { get; set; }
+        public double Strength { get; set; }
+
+        public PrimitiveMaterial()
+        {
+            Id = Convert.ToString(Guid.NewGuid());
+        }
+    }
+}