package main

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

const MOD = 1000000007

func power(base, exp int64) int64 {
	res := int64(1)
	base %= MOD
	for exp > 0 {
		if exp%2 == 1 {
			res = (res * base) % MOD
		}
		base = (base * base) % MOD
		exp /= 2
	}
	return res
}

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

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

	for i := 0; i < t; i++ {
		var n int
		fmt.Fscan(in, &n)

		var sum, sumSq int64
		for j := 0; j < n; j++ {
			var val int64
			fmt.Fscan(in, &val)
			val %= MOD
			sum = (sum + val) % MOD
			sumSq = (sumSq + val*val) % MOD
		}

		num := (sum*sum - sumSq) % MOD
		if num < 0 {
			num += MOD
		}

		den := (int64(n) % MOD * int64(n-1) % MOD) % MOD
		ans := (num * power(den, MOD-2)) % MOD

		fmt.Fprintln(out, ans)
	}
}