#include<bits/stdc++.h>
#define ll long long
#define mk make_pair
#define fi first
#define se second
#define pii pair<int,int>
#define eb emplace_back
using namespace std;
ll read(){
	ll X = 0,r = 1;
	char ch = getchar();
	while(!isdigit(ch) && ch != '-') ch = getchar();
	if(ch == '-') r = -1,ch = getchar();
	while(isdigit(ch)) X = X*10+ch-'0',ch = getchar();
	return X*r;
}
const int N = 110;
const int dx[9] = {0,0,0,1,-1,1,-1,1,-1};
const int dy[9] = {0,1,-1,0,0,1,-1,-1,1};
const int inf = 1e9;
int n,m;
int mp[N][N];
int black[N][N],white[N][N],cnt,S,T;
bool chk1(int x,int y){
	if(mp[x][y] == 0 || mp[x+1][y] == 0 || mp[x][y+1] == 0 || mp[x+1][y+1] == 0) return false;
	return true;
}
bool chk2(int x,int y){
	if(mp[x][y] == 1 || mp[x+1][y] == 1 || mp[x][y+1] == 1 || mp[x+1][y+1] == 1) return false;
	return true;
}
const int M = 2e6+10;
int head[M],nxt[M],to[M],edge[M],tot;
void add_edge(int u,int v,int w){
//	cout << u << " " << v << " " << w << "\n";
	to[++tot] = v; nxt[tot] = head[u];
	head[u] = tot; edge[tot] = w;
	to[++tot] = u; nxt[tot] = head[v];
	head[v] = tot; edge[tot] = 0;
}
int dep[M],now[M];
bool bfs(){
	for(int i=0;i<=cnt;i++) dep[i] = 0; 
	queue<int> q;
	q.push(S);
	now[S] = head[S]; dep[S] = 1;
	while(!q.empty()){
		int x = q.front(); q.pop();
		for(int i=head[x];i;i=nxt[i]){
			int y = to[i];
			if(dep[y] || !edge[i]) continue;
			dep[y] = dep[x]+1;
			now[y] = head[y];
			if(y == T) return true;
			q.push(y);
		}
	}
	return false;
}
int dinic(int x,int flow){
	if(x == T) return flow;
	int rest = flow;
	for(int i=now[x];i && rest;i=nxt[i]){
		now[x] = i;
		int y = to[i];
		if(dep[y] != dep[x]+1 || !edge[i]) continue;
		int k = dinic(y,min(rest,edge[i]));
		if(!k) dep[y] = 0;
		edge[i] -= k;
		rest -= k;
		edge[i^1] += k;
	}
	return flow-rest;
}

int main(){
	int TTT = read();
	while(TTT--){
		n = read(); m = read();
		for(int i=1;i<=n;i++)
			for(int j=1;j<=m;j++){
				char ch; cin >> ch;
				if(ch == 'W') mp[i][j] = 0;
				else if(ch == 'B') mp[i][j] = 1;
				else mp[i][j] = 2;
				if(((i+j) & 1) && mp[i][j] != 2) mp[i][j] ^= 1;
			}
		S = 0; T = 1; cnt = 1;
		
		for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) black[i][j] = white[i][j] = 0;
		for(int i=1;i<n;i++)
			for(int j=1;j<m;j++){
				if(chk1(i,j)) black[i][j] = ++cnt;
				if(chk2(i,j)) white[i][j] = ++cnt;
			}
//		for(int i=1;i<=n;i++){
//			for(int j=1;j<=m;j++) cout << white[i][j] << " ";
//			cout << "\n";
//		}
		for(int i=0;i<=cnt;i++) head[i] = 0;
		tot = 1; 
		for(int i=1;i<n;i++){
			for(int j=1;j<m;j++){
				if(chk1(i,j)) add_edge(S,black[i][j],1);
				if(chk2(i,j)) add_edge(white[i][j],T,1);
				if(!black[i][j]) continue;
				for(int k=0;k<9;k++){
					int x = i+dx[k],y = j+dy[k];
					if(!white[x][y]) continue;
					add_edge(black[i][j],white[x][y],inf);
				}
			}
		}
		int flow = 0;
		while(bfs()) flow += dinic(S,inf);
		cout << cnt-1-flow << "\n";
		for(int i=1;i<n;i++)
			for(int j=1;j<m;j++) if(black[i][j]){
				int x = black[i][j];
				for(int I=head[x];I;I=nxt[I]){
					int y = to[I];
					if(y != S || edge[I]) continue;
					mp[i][j] = mp[i+1][j] = mp[i][j+1] = mp[i+1][j+1] = 1;
				}
			}
		for(int i=1;i<n;i++)
			for(int j=1;j<m;j++) if(white[i][j]){
				int x = white[i][j];
				for(int I=head[x];I;I=nxt[I]){
					int y = to[I];
					if(y != T || !edge[I]) continue;
					mp[i][j] = mp[i+1][j] = mp[i][j+1] = mp[i+1][j+1] = 0;
				}
			}
		for(int i=1;i<=n;i++){
			for(int j=1;j<=m;j++){
				if(mp[i][j] == 2) mp[i][j] = 0;
				if((i+j) & 1) mp[i][j] = mp[i][j]^1;
				if(mp[i][j]) putchar('B');
				else putchar('W');
			}
			cout << "\n";
		}
	}
	return 0;
}