Add test on registration on non empty object

Author: vallsv

lib/matplotlib/tests/test_cbook.py

@@ -261,6 +261,32 @@ def test_callback_wrong_disconnect(self):
         # check we still have callbacks registered
         self.is_not_empty()
 
+    @pytest.mark.xfail(reason="must be fixed")
+    def test_registration_on_non_empty_registry(self):
+        # ensure we start with an empty registry
+        self.is_empty()
+
+        # setup the registry with a callback
+        mini_me = Test_callback_registry()
+        self.connect(self.signal, mini_me.dummy)
+
+        # Add another callback
+        mini_me2 = Test_callback_registry()
+        self.connect(self.signal, mini_me2.dummy)
+
+        # Remove and add the second callback
+        mini_me2 = Test_callback_registry()
+        self.connect(self.signal, mini_me2.dummy)
+
+        # We still have 2 references
+        self.is_not_empty()
+        assert self.count() == 2
+
+        # Removing the last 2 references
+        mini_me = None
+        mini_me2 = None
+        self.is_empty()
+
     def dummy(self):
         pass