#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef __int128 i128;
typedef double db;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<int,ll> pil;
typedef pair<ll,int> pli;
template <typename Type>
using vec=vector<Type>;
template <typename Type>
using grheap=priority_queue<Type>;
template <typename Type>
using lrheap=priority_queue<Type,vector<Type>,greater<Type> >;
#define fir first
#define sec second
#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define chmax(a,b) a=max(a,b)
#define chmin(a,b) a=min(a,b)
#define rep(i,x,y) for(int i=x;i<=y;i++)
#define per(i,x,y) for(int i=x;i>=y;i--)
#define id(x,y,k) (((x)-1)*(m-1)+(y)+((k)?((n-1)*(m-1)):0))

const int inf=0x3f3f3f3f;
const ll INF=0x3f3f3f3f3f3f3f3f;
const int mod=998244353;

const int N=100*100*2+1+5;
const int M=N*10;

struct Dinic{
    int n,cnt;
    int hd[N],fr[N];
    struct edge{
        int ne,to;
        ll cap,flow;
    }ed[M*2];
    int dp[N];
    queue<int> q;

    void init(int num){
        n=num;
        cnt=0;
        rep(i,0,n)hd[i]=-1;
    }
    void adde(int a,int b,ll cap){
        ed[cnt].ne=hd[a];hd[a]=cnt;
        ed[cnt].to=b;
        ed[cnt].cap=cap;
        ed[cnt].flow=0;
        cnt++;
        ed[cnt].ne=hd[b];hd[b]=cnt;
        ed[cnt].to=a;
        ed[cnt].cap=0;
        ed[cnt].flow=0;
        cnt++;
    }
    int bfs(int s,int t){
        rep(i,0,n)dp[i]=0;
        dp[s]=1;
        q.push(s);
        while(!q.empty()){
            int now=q.front();q.pop();
            for(int e=hd[now];~e;e=ed[e].ne){
                int nxt=ed[e].to;
                if(ed[e].cap>ed[e].flow&&!dp[nxt]){
                    dp[nxt]=dp[now]+1;
                    q.push(nxt);
                }
            }
        }
        return dp[t];
    }
    ll dfs(int now,int t,ll flow){
        if(now==t||!flow)return flow;
        ll res=0;
        for(int &e=fr[now];~e;e=ed[e].ne){
            int nxt=ed[e].to;
            if(ed[e].cap>ed[e].flow&&dp[nxt]==dp[now]+1){
                ll f=dfs(nxt,t,min(flow-res,ed[e].cap-ed[e].flow));
                res+=f;
                ed[e].flow+=f;
                ed[e^1].flow-=f;
                if(res==flow)break;
            }
        }
        return res;
    }
    ll maxflow(int s,int t){
        ll res=0;
        while(bfs(s,t)){
            rep(i,0,n)fr[i]=hd[i];
            res+=dfs(s,t,INF);
        }
        return res;
    }
}dc;

const int NN=105;

int n,m;
char g[NN][NN];

bool check(int i,int j,int k){
    if(k)return (g[i][j]=='B'||g[i][j]=='?')&&(g[i][j+1]=='B'||g[i][j+1]=='?')&&(g[i+1][j]=='B'||g[i+1][j]=='?')&&(g[i+1][j+1]=='B'||g[i+1][j+1]=='?');
    else return (g[i][j]=='W'||g[i][j]=='?')&&(g[i][j+1]=='W'||g[i][j+1]=='?')&&(g[i+1][j]=='W'||g[i+1][j]=='?')&&(g[i+1][j+1]=='W'||g[i+1][j+1]=='?');
}

bool can[NN][NN];
char ans[NN][NN];
void print(int i,int j,int k){
    if(k==1){
        if(i+j&1)ans[i][j]='W',ans[i+1][j]='B',ans[i][j+1]='B',ans[i+1][j+1]='W';
        else ans[i][j]='B',ans[i+1][j]='W',ans[i][j+1]='W',ans[i+1][j+1]='B';
    }else{
        if(i+j&1)ans[i][j]='B',ans[i+1][j]='W',ans[i][j+1]='W',ans[i+1][j+1]='B';
        else ans[i][j]='W',ans[i+1][j]='B',ans[i][j+1]='B',ans[i+1][j+1]='W';
    }
}

void solve(){
    cin>>n>>m;
    int s=0,t=id(n,m,1)+1;
    dc.init(t);
    rep(i,1,n)rep(j,1,m){
        cin>>g[i][j];
        ans[i][j]=0;
        if(i+j&1){
            if(g[i][j]=='B')g[i][j]='W';
            else if(g[i][j]=='W')g[i][j]='B';
        }
    }
    ll cnt=0;
    rep(i,1,n-1)rep(j,1,m-1){
        if(check(i,j,0)){
            cnt++;
            dc.adde(s,id(i,j,0),1);
            dc.adde(id(i,j,0),id(i,j,1),INF);
            if(j<m-1)dc.adde(id(i,j,0),id(i,j+1,1),INF);
            if(i<n-1)dc.adde(id(i,j,0),id(i+1,j,1),INF);
            if(i<n-1&&j<m-1)dc.adde(id(i,j,0),id(i+1,j+1,1),INF);
            if(i>1&&j<m-1)dc.adde(id(i,j,0),id(i-1,j+1,1),INF);
        }
        if(check(i,j,1)){
            cnt++;
            dc.adde(id(i,j,1),t,1);
            dc.adde(id(i,j,0),id(i,j,1),INF);
            if(j<m-1)dc.adde(id(i,j+1,0),id(i,j,1),INF);
            if(i<n-1)dc.adde(id(i+1,j,0),id(i,j,1),INF);
            if(i<n-1&&j<m-1)dc.adde(id(i+1,j+1,0),id(i,j,1),INF);
            if(i>1&&j<m-1)dc.adde(id(i-1,j+1,0),id(i,j,1),INF);
        }
    }
    cout<<cnt-dc.maxflow(s,t)<<"\n";
    rep(i,1,n-1)rep(j,1,m-1){
        if(check(i,j,0)&&dc.dp[id(i,j,0)])print(i,j,0);
        if(check(i,j,1)&&!dc.dp[id(i,j,1)])print(i,j,1);
    }
    rep(i,1,n){
        rep(j,1,m){
            if(!ans[i][j]){
                if(g[i][j]=='?')cout<<'B';
                else{
                    if(i+j&1)cout<<(g[i][j]=='B'?'W':'B');
                    else cout<<g[i][j];
                }
            }
            else cout<<ans[i][j];
        }cout<<"\n";
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    int t;cin>>t;
    while(t--)solve();
    return 0;
}