Add test for issue #11615

IPython/core/tests/test_interactiveshell.py

@@ -449,6 +449,24 b' class InteractiveShellTestCase(unittest.TestCase):'
             # Reset the custom exception hook
             ip.set_custom_exc((), None)
     
+    @mock.patch('builtins.print')
+    def test_showtraceback_with_surrogates(self, mocked_print):
+        values = []
+        def mock_print_func(value, sep=' ', end='\n', file=sys.stdout, flush=False):
+            values.append(value)
+            if value == chr(0xd8ff):
+                raise UnicodeEncodeError("utf-8", chr(0xd8ff), 0, 1, "")
+
+        # mock builtins.print
+        mocked_print.side_effect = mock_print_func
+
+        # ip._showtraceback() is replaced in globalipapp.py. 
+        # Call original method to test.
+        interactiveshell.InteractiveShell._showtraceback(ip, None, None, chr(0xd8ff))
+        
+        self.assertEqual(mocked_print.call_count, 2)
+        self.assertEqual(values, [chr(0xd8ff), '\\ud8ff'])
+
     def test_mktempfile(self):
         filename = ip.mktempfile()
         # Check that we can open the file again on Windows