// Test passes, move on to next feature
test('calculates order total with tax', () => {
  const order = { items: [{ price: 100 }, { price: 50 }], taxRate: 0.1 }
  expect(calculateTotal(order)).toBe(165)
})

// Quick and dirty implementation, "will clean up later"
function calculateTotal(order: Order): number {
  let t = 0
  for (let i = 0; i < order.items.length; i++) {
    t = t + order.items[i].price
  }
  t = t + t * order.taxRate
  return t
}
// Technical debt: unclear variable names, imperative style

test('calculates order total with tax', () => {
  const order = { items: [{ price: 100 }, { price: 50 }], taxRate: 0.1 }
  expect(calculateTotal(order)).toBe(165)
})

// After GREEN, immediately refactor
function calculateTotal(order: Order): number {
  const subtotal = order.items.reduce((sum, item) => sum + item.price, 0)
  const tax = subtotal * order.taxRate
  return subtotal + tax
}
// Clean: descriptive names, functional style, clear intent