#include<bits/stdc++.h>
#define LL long long
#define LLL __int128
#define uint unsigned
#define ldb long double
#define uLL unsigned long long
using namespace std;
char wS[262144],rdc[262144],*rS,*rT,*wT=wS;
#define gc() (rS==rT?rT=rdc+fread(rS=rdc,1,262144,stdin),rS==rT?EOF:*rS++:*rS++)
#define flush() fwrite(wS,1,wT-wS,stdout),wT=wS
inline void pc(const char&x){*wT++=x;if(__builtin_expect(wS+262144==wT,0))flush();}
template<class T=int>inline T read(){
    T x(0);char c;bool f(1);while(!isdigit(c=gc()))if(c==45)f=!f;
    if(f)do x=x*10+(c&15);while(isdigit(c=gc()));
    else do x=x*10-(c&15);while(isdigit(c=gc()));
    return x;
}
template<>inline void read(){while(gc()<33);while(gc()>32);}
template<>inline char read(){char c;while((c=gc())<33);return c;}
template<>inline string read(){char c;string s;while((c=gc())<33);do s+=c;while((c=gc())>32);return s;}
inline int read(char*const s){char c,*t=s;while((c=gc())<33);do *t++=c;while((c=gc())>32);return *t=0,t-s;}
template<class T>inline void write(T x){
    int o=0;char _[50];
    if(x>=0)do _[o++]=(x%10)|48;while(x/=10);
    else{pc(45);do _[o++]=-(x%10)|48;while(x/=10);}
    for(;o;pc(_[--o]));
}
template<>inline void write(char x){pc(x);}
template<>inline void write(char*s){for(;*s;pc(*s++));}
template<>inline void write(const char*s){for(;*s;pc(*s++));}
template<class T>inline void write(const basic_string<T>&x){for(auto c:x)write(c);}
template<class T>inline void write(const initializer_list<T>&x){for(auto c:x)write(c),pc(32);}
template<class T,class...U>inline void write(const T&x,const U&...y){write(x),write(y...);}
const int N=2e4+5,M=3e5+5,INF=1e7;
int n,m,s=0,t=1,iT;
char a[105][105];
struct edge{int v,w,nxt;}e[M];
int em,h[N],cur[N],d[N],gap[N],vs[N];
inline void add(const int&u,const int&v,const int&w){
    e[++em]={v,w,h[u]},h[u]=em;
    e[++em]={u,0,h[v]},h[v]=em;
}
inline void clear(const int&__n){
    em=1;
    memset(h,0,__n<<2);
    memset(d,-1,__n<<2);
    memset(gap,0,__n<<2);
}
inline void bfs(){
    int ql=0,qr=1;
    static int Q[N];
    for(d[Q[1]=t]=0;ql<qr;){
        int u=Q[++ql];
        for(int i=h[u],v;i;i=e[i].nxt)
            if(e[i^1].w&&d[v=e[i].v]==-1)
                ++gap[d[Q[++qr]=v]=d[u]+1];
    }
}
inline int dfs(const int&u,int mf){
    if(u==t)return mf;
    if(d[u]==-1)return 0;
    int res=0;
    for(int i=cur[u];cur[u]=i;i=e[i].nxt){
        int v=e[i].v,w=e[i].w;
        if(d[v]+1==d[u]&&w){
            int dd=dfs(v,min(mf,w));
            e[i].w-=dd,mf-=dd,e[i^1].w+=dd,res+=dd;
            if(!mf)return res;
        }
    }
    if(~d[u]&&!--gap[d[u]])d[s]=-1;
    if(~d[u])++gap[++d[u]];
    return res;
}
inline int isap(const int&__n){
    int ans=0;
    for(bfs();~d[s];ans+=dfs(s,INF))memcpy(cur,h,__n<<2);
    return ans;
}
inline void dfs_(const int&u,const int&c){
    vs[u]=c;
    for(int i=h[u];i;i=e[i].nxt)
        if(e[i].w&&vs[e[i].v]!=c)dfs_(e[i].v,c);
}
inline int idx(const int&x,const int&y,const int&z){
    return z*(n-1)*(m-1)+1+(x-1)*(m-1)+y;
}
inline void MAIN(){
    n=read(),m=read(),clear((n-1)*(m-1)*2+2);
    for(int i=1;i<=n;++i)read(a[i]+1);
    for(int i=1;i<=n;++i)
        for(int j=1;j<=m;++j)
            if(((i^j)&1)&&isalpha(a[i][j]))a[i][j]^='B'^'W';
    int ans=0;
    for(int i=1;i<n;++i)
        for(int j=1;j<m;++j){
            if(a[i][j]!='W'&&a[i+1][j]!='W'&&a[i][j+1]!='W'&&a[i+1][j+1]!='W')add(s,idx(i,j,0),1),++ans;
            if(a[i][j]!='B'&&a[i+1][j]!='B'&&a[i][j+1]!='B'&&a[i+1][j+1]!='B')add(idx(i,j,1),t,1),++ans;
            for(int _i=max(1,i-1);_i<=min(n-1,i+1);++_i)
                for(int _j=max(1,j-1);_j<=min(m-1,j+1);++_j)
                    add(idx(i,j,0),idx(_i,_j,1),INF);
        }
    write(ans-isap((n-1)*(m-1)*2+2),'\n'),dfs_(s,++iT);
    for(int i=1;i<n;++i)
        for(int j=1;j<m;++j)
            if(vs[idx(i,j,0)]==iT)
                a[i][j]=a[i+1][j]=a[i][j+1]=a[i+1][j+1]='B';
    for(int i=1;i<=n;++i){
        for(int j=1;j<=m;++j){
            if(!isalpha(a[i][j]))a[i][j]='W';
            if((i^j)&1)a[i][j]^='B'^'W';
        }
        write(a[i]+1,'\n');
    }
}
signed main(){
    cin.tie(0)->sync_with_stdio(0);
#define LOCAL
#ifndef LOCAL
    freopen(".in","r",stdin);
    freopen(".out","w",stdout);
#endif
    for(int T=read();T--;MAIN());
    return flush(),0;
}
/*
*/