Fix successor test cases

runall.py

@@ -77,7 +77,6 @@ def find_script(pairs, max_length):
 
 
 if __name__ == '__main__':
-    # Identity
     print("\nSearching for identity")
     find_script((
         ("1", "1"),
@@ -85,10 +84,9 @@ if __name__ == '__main__':
         ("1984", "1984"),
     ), max_length=3)
 
-    # Successor
-    # print("\nSearching for successor")
-    # find_script((
-    #     ("1", "2"),
-    #     ("2", "3"),
-    #     ("3", "4"),
-    # ), max_length=5)
+    print("\nSearching for successor")
+    find_script((
+        ("1", "2"),
+        ("42", "43"),
+        ("1984", "1985"),
+    ), max_length=5)