TST: add test for searching for removal with bare functions

IPython/core/tests/test_events.py

@@ -1,73 +1,85 b''
 from backcall import callback_prototype
 import unittest
 from unittest.mock import Mock
+import nose.tools as nt
 
 from IPython.core import events
 import IPython.testing.tools as tt
 
 
 @events._define_event
 def ping_received():
     pass
 
 
 @events._define_event
 def event_with_argument(argument):
     pass
 
 
 class CallbackTests(unittest.TestCase):
     def setUp(self):
         self.em = events.EventManager(get_ipython(), {'ping_received': ping_received, 'event_with_argument': event_with_argument})
     
     def test_register_unregister(self):
         cb = Mock()
 
         self.em.register('ping_received', cb)        
         self.em.trigger('ping_received')
         self.assertEqual(cb.call_count, 1)
         
         self.em.unregister('ping_received', cb)
         self.em.trigger('ping_received')
         self.assertEqual(cb.call_count, 1)
-    
+
+    def test_bare_function_missed_unregister(self):
+        def cb1():
+            ...
+
+        def cb2():
+            ...
+
+        self.em.register('ping_received', cb1)
+        nt.assert_raises(ValueError, self.em.unregister, 'ping_received', cb2)
+        self.em.unregister('ping_received', cb1)
+
     def test_cb_error(self):
         cb = Mock(side_effect=ValueError)
         self.em.register('ping_received', cb)
         with tt.AssertPrints("Error in callback"):
             self.em.trigger('ping_received')
 
     def test_unregister_during_callback(self):
         invoked = [False] * 3
         
         def func1(*_):
             invoked[0] = True
             self.em.unregister('ping_received', func1)
             self.em.register('ping_received', func3)
 
         def func2(*_):
             invoked[1] = True
             self.em.unregister('ping_received', func2)
 
         def func3(*_):
             invoked[2] = True
             
         self.em.register('ping_received', func1)
         self.em.register('ping_received', func2)
 
         self.em.trigger('ping_received')
         self.assertEqual([True, True, False], invoked)
         self.assertEqual([func3], self.em.callbacks['ping_received'])
     
     def test_ignore_event_arguments_if_no_argument_required(self):
         call_count = [0]
         def event_with_no_argument():
             call_count[0] += 1
 
         self.em.register('event_with_argument', event_with_no_argument)
         self.em.trigger('event_with_argument', 'the argument')
         self.assertEqual(call_count[0], 1)
         
         self.em.unregister('event_with_argument', event_with_no_argument)
         self.em.trigger('ping_received')
         self.assertEqual(call_count[0], 1)