This run_test helper sets up a convention that allows
us to give really short tracebacks for errors, and
eventually we can have more control over running
individual tests. (The latter goal has some
complications, since we often intentionally leak
setup in tests.)
The new list_cursor class is more generic and saves the state
of your cursor across redraws.
Note that we no longer cycle from bottom to top or vice versa.
The node test code that was removed here was kind of complex
and didn't actually assert useful things after calling methods.
This node test module is intended as a way for somebody to
quickly immerse themselves in our node testing methodologies,
plus it has the nice side effect of introducing several modules
(albeit very briefly).