Add additional test case + update missing del tests

python/ql/test/query-tests/Classes/missing-del/missing_del.py

@@ -2,14 +2,19 @@
 class X1(object):
 
     def __del__(self):
-        pass
+        print("X1 del")
 
 class X2(X1):
 
     def __del__(self):
+        print("X2 del")
         X1.__del__(self)
 
-class X3(X2):
+class X3(X2):  # $ Alert - skips X2 del
 
     def __del__(self):
+        print("X3 del")
         X1.__del__(self)
+
+a = X3()
+del a