Add test for virtual method dispatch

Author: BrzVlad

src/tests/JIT/interpreter/Interpreter.cs

@@ -4,6 +4,33 @@
 using System;
 using System.Runtime.CompilerServices;
 
+public interface ITest
+{
+    public int VirtualMethod();
+}
+
+public class BaseClass : ITest
+{
+    public int NonVirtualMethod()
+    {
+        return 0xbaba;
+    }
+
+    public virtual int VirtualMethod()
+    {
+        return 0xbebe;
+    }
+}
+
+public class DerivedClass : BaseClass
+{
+    public override int VirtualMethod()
+    {
+        return 0xdede;
+    }
+
+}
+
 public struct MyStruct
 {
     public int a;
@@ -71,6 +98,8 @@ public static void RunInterpreterTests()
 //            Environment.FailFast(null);
         if (!TestFloat())
             Environment.FailFast(null);
+        if (!TestVirtual())
+            Environment.FailFast(null);
     }
 
     public static int Mul4(int a, int b, int c, int d)
@@ -209,4 +238,26 @@ public static bool TestFloat()
 
         return true;
     }
+
+    public static bool TestVirtual()
+    {
+        BaseClass bc = new DerivedClass();
+        ITest itest = bc;
+
+        if (bc.NonVirtualMethod() != 0xbaba)
+            return false;
+        if (bc.VirtualMethod() != 0xdede)
+            return false;
+        if (itest.VirtualMethod() != 0xdede)
+            return false;
+        bc = new BaseClass();
+        itest = bc;
+        if (bc.NonVirtualMethod() != 0xbaba)
+            return false;
+        if (bc.VirtualMethod() != 0xbebe)
+            return false;
+        if (itest.VirtualMethod() != 0xbebe)
+            return false;
+        return true;
+    }
 }