package main

import (
	"bytes"
	"io"
	"os"
)

func main() {
	data, _ := io.ReadAll(os.Stdin)
	p := 0

	nextInt := func() int {
		for p < len(data) && data[p] <= ' ' {
			p++
		}
		v := 0
		for p < len(data) && data[p] > ' ' {
			v = v*10 + int(data[p]-'0')
			p++
		}
		return v
	}

	nextString := func() string {
		for p < len(data) && data[p] <= ' ' {
			p++
		}
		start := p
		for p < len(data) && data[p] > ' ' {
			p++
		}
		return string(data[start:p])
	}

	tc := nextInt()
	var out bytes.Buffer

	for ; tc > 0; tc-- {
		_ = nextInt()
		_ = nextInt()
		s := nextString()
		t := nextString()

		var pos [26][]int
		for i := 0; i < len(s); i++ {
			c := int(s[i] - 'a')
			pos[c] = append(pos[c], i+1)
		}

		var idx [26]int
		var lb [26]int
		ok := true

		for i := 0; i < len(t); i++ {
			c := int(t[i] - 'a')
			j := idx[c]
			list := pos[c]
			for j < len(list) && list[j] <= lb[c] {
				j++
			}
			if j == len(list) {
				ok = false
				break
			}
			chosen := list[j]
			idx[c] = j + 1
			for d := 0; d < c; d++ {
				if lb[d] < chosen {
					lb[d] = chosen
				}
			}
		}

		if ok {
			out.WriteString("YES\n")
		} else {
			out.WriteString("NO\n")
		}
	}

	os.Stdout.Write(out.Bytes())
}