Subclass item to do useful things.
Add equality test.
Verify that comparison of UsefulItem lists works.
Wrap long line.
Basic behaviour test to move update logic into UsefulItem.
Move update code into UsefulItem.
Map over items.
Fix indentation.
Reformat equality method.
Turn update into a function.
Remove unnecessary newlines.
Add Brie tests
Extract Brie behaviour.
Add Sulfuras test.
Implement sulfuras update,
Correct Brie test name.
Add backstage pass test cases.
Missing some test cases for original Brie code; revert.
Added more Brie tests covering double quality after sell by date.
Bleh. Update brie works, but is janky.