Two kind of mistakes:
1. Missed space. After concatenating there is no space between words.
2. Missed comma. Causes unintentional concatenating in a list of strings.
Fix bug in existing human test and add instructions; fix two bugs in tested
code; remove redundancies, add spaces, and change two internal method names.
Add mock_tk with mocks for tkinter.Variable subclasses and tkinter.messagebox.
Use mocks in test_config_name to unittest methods that are otherwise gui-free.