```go
package main

import (
	"bufio"
	"fmt"
	"os"
)

type MaxHeap struct {
	id  []int
	val []int
}

func (h *MaxHeap) Len() int { return len(h.id) }
func (h *MaxHeap) less(i, j int) bool {
	if h.val[i] != h.val[j] {
		return h.val[i] > h.val[j]
	}
	return h.id[i] < h.id[j]
}
func (h *MaxHeap) swap(i, j int) {
	h.id[i], h.id[j] = h.id[j], h.id[i]
	h.val[i], h.val[j] = h.val[j], h.val[i]
}
func (h *MaxHeap) up(i int) {
	for i > 0 {
		p := (i - 1) / 2
		if !h.less(i, p) {
			break
		}
		h.swap(i, p)
		i = p
	}
}
func (h *MaxHeap) down(i int) {
	n := h.Len()
	for {
		l := i*2 + 1
		if l >= n {
			break
		}
		best := l
		r := l + 1
		if r < n && h.less(r, l) {
			best = r
		}
		if !h.less(best, i) {
			break
		}
		h.swap(i, best)
		i = best
	}
}
func (h *MaxHeap) Push(id, val int) {
	h.id = append(h.id, id)
	h.val = append(h.val, val)
	h.up(h.Len() - 1)
}
func (h *MaxHeap) Pop() (id, val int) {
	n := h.Len()
	id, val = h.id[0], h.val[0]
	last := n - 1
	h.id[0], h.val[0] = h.id[last], h.val[last]
	h.id = h.id[:last]
	h.val = h.val[:last]
	if h.Len() > 0 {
		h.down(0)
	}
	return
}

type Pair struct{ i, j int }

func main() {
	in := bufio.NewReaderSize(os.Stdin, 1<<20)
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	var t int
	fmt.Fscan(in, &t)

	for ; t > 0; t-- {
		var n int
		fmt.Fscan(in, &n)
		h := &MaxHeap{}
		for i := 1; i <= n; i++ {
			var a int
			fmt.Fscan(in, &a)
			if a > 0 {
				h.Push(i, a)
			}
		}

		res := make([]Pair, 0)
		for h.Len() >= 2 {
			i1, v1 := h.Pop()
			i2, v2 := h.Pop()
			res = append(res, Pair{i1, i2})
			v1--
			v2--
			if v1 > 0 {
				h.Push(i1, v1)
			}
			if v2 > 0 {
				h.Push(i2, v2)
			}
		}

		fmt.Fprintln(out, len(res))
		for _, p := range res {
			fmt.Fprintln(out, p.i, p.j)
		}
	}
}
```