Issue #18830: inspect.getclasstree() no more produces duplicated entries even
when input list contains duplicates.
diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py
index 04dcfe9..4130cd0 100644
--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -220,8 +220,23 @@
                          [('FesteringGob', mod.FesteringGob),
                           ('MalodorousPervert', mod.MalodorousPervert),
                           ('ParrotDroppings', mod.ParrotDroppings),
-                          ('StupidGit', mod.StupidGit)])
-        tree = inspect.getclasstree([cls[1] for cls in classes], 1)
+                          ('StupidGit', mod.StupidGit),
+                          ('Tit', mod.MalodorousPervert),
+                         ])
+        tree = inspect.getclasstree([cls[1] for cls in classes])
+        self.assertEqual(tree,
+                         [(mod.ParrotDroppings, ()),
+                          [(mod.FesteringGob, (mod.MalodorousPervert,
+                                                  mod.ParrotDroppings))
+                           ],
+                          (mod.StupidGit, ()),
+                          [(mod.MalodorousPervert, (mod.StupidGit,)),
+                           [(mod.FesteringGob, (mod.MalodorousPervert,
+                                                   mod.ParrotDroppings))
+                            ]
+                           ]
+                          ])
+        tree = inspect.getclasstree([cls[1] for cls in classes], True)
         self.assertEqual(tree,
                          [(mod.ParrotDroppings, ()),
                           (mod.StupidGit, ()),