Spree::Order#variant should trigger update!

output.txt

Subtotal: 0.0
Total: 0.0

Spree Bag: 22.99
Subtotal: 0.0
Total: 0.0

scratch.rb

def totals(order)
  order.line_items.each do |item|
    puts "#{item.variant.name}: #{item.amount}"
  end
  puts "Subtotal: #{order.item_total}"
  puts "Total: #{order.total}"
end

order = Spree::Order.create!
totals(order)
puts

order.add_variant(Spree::Variant.find_by_sku('SPR-00012'))
totals(order)
puts