So far, we've done well with patch, Mock, and the default TestCase, but testing our widgets module is going to present some new challenges. To begin with, our widgets will need a Tk instance to be their root window. We can create this in each case's setUp() method, but this will slow down the tests considerably, and it isn't really necessary; our tests aren't going to modify the root window, so one root window will suffice for each test case. We can take advantage of the setUpClass() method to create a single instance of Tk just once at class instantiation. Secondly, we have a large number of widgets to test, which means we have a large number of test cases requiring the same boilerplate Tk() setup and tear down.
To address ...
