See https://github.com/ArturT/GildedRose-Refactoring-Kata

gilded_rose_edge_case.rb

it 'increases to 50 when sell_in above 10 and quality is 49' do
  item = Item.new('Backstage passes to a TAFKAL80ETC concert', sell_in=15, quality=49)
  items = [item]
  gilded_rose = described_class.new(items)
  gilded_rose.update_quality

  expect(item.quality).to eq 50
end

it 'increases to 50 instead of 51 when sell_in at least 5 and quality is 49' do
  item = Item.new('Backstage passes to a TAFKAL80ETC concert', sell_in=5, quality=49)
  items = [item]
  gilded_rose = described_class.new(items)
  gilded_rose.update_quality

  expect(item.quality).to eq 50
end