Writing Benchmarks

The benchmark below compiles, runs, and prints a believable number, and that number is wrong. It measures the total of an order with 100 items, and each item needs a multiplication and a tax calculation.

// file: order.go
package order

import (
	"fmt"
	"strings"
)

type Item struct {
	SKU      string
	Quantity int
	Cents    int64 // price of one unit, in cents
}

type Order struct {
	ID       int64
	Customer string
	Items    []Item
	Paid     bool
}

// LineCents returns one line's price plus 7.5 percent tax, rounded up.
func (i Item) LineCents() int64 {
	line := int64(i.Quantity) * i
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