For test_textview, I triggered the symptom -- 4 'TV' NameErrors on re-run, by (temporarily) adding 1/0 to tearDownModule and running with -w. After removing the TV deletion, only the ZeroDivisionError remained. This experiment also resulted in a '''can't invoke "event" command: application has been destroyed''' message. For me it only happens on the re-run, not in the first run. In verbose mode, it follows the one test in test_config_key. Converting the test to 'pass' proved it to be the source. Looking at the code, I could not find any obvious callback that would be left behind. Adding 'root.update() stops the message. (Adding root.update_idletasks() did not.) In the output quoted above, the same message is shown for the non-verbose initial run, If from the same cause, the same fix might work on Mac also.