feat: add new tests

tests/programs/pos_class.fzs

@@ -0,0 +1,25 @@
+class Point
+{
+  int x;
+  int y;
+
+  fn move(int dx, int dy)
+  {
+    this.x = this.x + dx;
+    this.y = this.y + dy;
+  }
+}
+
+Point point = new Point;
+point.x = 1;
+point.y = 2;
+point.move(9, 8);
+
+if (point.x == 10 && point.y == 10)
+  printline("class method passed");
+else
+{
+  printline("class method failed");
+  exit(1);
+}
+