In general we want to mimimize the amount of setup at the top
of a test module and just let individual tests explicitly
mock what they need to mock.
The `override` helper has the advantage that it avoids dead
code. For example, if the way we invoked the list widget
here no longer required sorting, the unit tests would complain
about the crufty override, whereas the previous code doesn't
really have that kind of future-proofing.
