* Add failing test for list widget with counter-last
The failing test appends a value to a list without changing the rest of
the list, and the counter-last value doesn't get updated correctly when
that happens. Also added another test, which passes, testing removing
the last item of the list, just in case of a regression.
* Improve unit tests for counter-last list widget bug
The unit tests were looking very similar to each other, so I factored
out the common code and made them into simple data-driven tests.
* Fix bug where counter-last fails in list widget
The only scenario that was failing was when counter-last was used, but
the list was strictly appended to with no other changes made. The one
unit test that was failing now passes with this fix.
* Improve bugfix to list widget counter-last
Now we only refresh the last item if it was truly necessary.
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