package main

import "fmt"

func main() {
	var T int
	fmt.Scan(&T)
	for tc := 1; tc <= T; tc++ {
		var R, C int
		fmt.Scan(&R, &C)
		cake := make([][]byte, R)
		stop := make([][]bool, R)
		for i := 0; i < R; i++ {
			fmt.Scan(&cake[i])
			stop[i] = make([]bool, C)
			for j, b := range cake[i] {
				stop[i][j] = b == '?'
			}
		}
		for r := 0; r < R; r++ {
			for c := 0; c < C; c++ {
				if stop[r][c] {
					continue
				}
				expand(cake, cake[r][c], R, C, r, c, r, c)
			}
		}
		fmt.Printf("Case #%d:\n", tc)
		for i := 0; i < R; i++ {
			fmt.Println(string(cake[i]))
		}
	}
}

// .--> x
// |
// |
// v
// y

func expand(cake [][]byte, init byte, R, C, r1, c1, r2, c2 int) {
	isExpand := false
	for 0 < c1 { // Left
		i := r1
		for ; i <= r2 && cake[i][c1-1] == '?'; i++ {
		}
		if i <= r2 {
			break
		}
		c1--
		for i = r1; i <= r2; i++ {
			cake[i][c1] = init
		}
		isExpand = true
	}
	for 0 < r1 { // Up
		i := c1
		for ; i <= c2 && cake[r1-1][i] == '?'; i++ {
		}
		if i <= c2 {
			break
		}
		r1--
		for i := c1; i <= c2; i++ {
			cake[r1][i] = init
		}
		isExpand = true
	}
	for c2 < C-1 { // Right
		i := r1
		for ; i <= r2 && cake[i][c2+1] == '?'; i++ {
		}
		if i <= r2 {
			break
		}
		c2++
		for i = r1; i <= r2; i++ {
			cake[i][c2] = init
		}
		isExpand = true
	}
	for r2 < R-1 { // Down
		i := c1
		for ; i <= c2 && cake[r2+1][i] == '?'; i++ {
		}
		if i <= c2 {
			break
		}
		r2++
		for i = c1; i <= c2; i++ {
			cake[r2][i] = init
		}
		isExpand = true
	}
	if isExpand {
		expand(cake, init, R, C, r1, c1, r2, c2)
	}
}