Add interpolation test.

src/Triangle.Examples/Examples/Example6.cs

@@ -13,7 +13,7 @@
     /// </summary>
     public static class Example6
     {
-        public static bool Run(bool print = true)
+        public static bool Run(bool print = false)
         {
             // Generate the input geometry.
             var polygon = new Polygon(8, true);

src/Triangle.Examples/Examples/ExamplePar.cs

@@ -76,7 +76,7 @@ namespace TriangleNet.Examples
                 Console.WriteLine("   Number of invalid triangulations: {0}", invalid);
             }
 
-            return true;
+            return invalid == 0;
         }
 
         private static void ProcessMesh(IMesh mesh, MeshResult result)