// Go in my style.
// Not afraid to dark.

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

clock_t sttime;
#define STCLOCK sttime = clock ();
#define TIMENOW fprintf (stderr, "\nNOW TIME COSSEMED: %0.4lf\n", 1.0 * (clock () - sttime) / CLOCKS_PER_SEC);
#define inline __inline__ __attribute__ ((always_inline))

namespace io {
    int read_pos, read_dt; char read_char;
    inline int read (int &p = read_pos){
        p = 0, read_dt = 1; read_char = getchar ();
        while (! isdigit (read_char)){
            if (read_char == '-')
                read_dt = - 1;
            read_char = getchar ();
        }
        while (isdigit (read_char)){
            p = (p << 1) + (p << 3) + read_char - 48;
            read_char = getchar ();
        }
        return p = p * read_dt;
    }
    int write_sta[65], write_top;
    inline void write (int x){
        if (x < 0)
            putchar ('-'), x = - x;
        write_top = 0;
        do
            write_sta[write_top ++] = x % 10, x /= 10;
        while (x);
        while (write_top)
            putchar (write_sta[-- write_top] + 48);
    }
    inline char next_blank (){
        static char c; c = getchar ();
        while (c != '?' && c != 'B' && c != 'W') c = getchar ();
        return c;
    }
}

const int N = 100, inf = 0x3f3f3f3f;
int n, m;
char a[N + 5][N + 5];

inline int vx (int i, int j, int o){
    return (i - 1) * m + j + o * n * m;
}
const int PS = N * N * 3 + 5, ES = N * N * 30 + 5;
struct Maxflow {
    int s, t, lrg;
    int firs[PS], nex[ES], to[ES], w[ES], tot;
    int cur[PS], dep[PS];
    bool inq[PS], inS[PS];
    inline void Add (int u, int v, int l, int _l_ = 0){
        nex[++ tot] = firs[u], firs[u] = tot, to[tot] = v, w[tot] = l;
        nex[++ tot] = firs[v], firs[v] = tot, to[tot] = u, w[tot] = _l_;
    }
    inline void init (){ tot = 1; for (int i = 0;i <= lrg;++ i) firs[i] = 0, inS[i] = false; }
    inline bool Bfs (){
        for (int i = 0;i <= lrg;++ i) cur[i] = firs[i], dep[i] = inf, inq[i] = false;
        queue < int > Q;
        Q.push (s); dep[s] = 0; inq[s] = true;
        while (! Q.empty ()){
            int u = Q.front (); Q.pop (); inq[u] = false;
            for (int e = firs[u], v;e;e = nex[e]){
                v = to[e];
                if (w[e] && dep[v] > dep[u] + 1){
                    dep[v] = dep[u] + 1;
                    if (! inq[v]){
                        inq[v] = true;
                        Q.push (v);
                    }
                }
            }
        }
        return dep[t] != inf;
    }
    int Dfs (int u, int flow){
        if (u == t) return flow;
        int used = 0, rlow;
        for (int &e = cur[u], v;e;e = nex[e]){
            v = to[e];
            if (w[e] && dep[v] == dep[u] + 1){
                rlow = Dfs (v, min (flow - used, w[e]));
                if (rlow){
                    w[e] -= rlow; w[e ^ 1] += rlow; used += rlow;
                    if (used == flow) break;
                }
            }
        }
        return used;
    }
    inline int FLOW (){
        static int Ansflow; Ansflow = 0;
        while (Bfs ()) Ansflow += Dfs (s, inf);
        return Ansflow;
    }
    void GET (int u){
        inS[u] = true;
        for (int e = firs[u], v;e;e = nex[e]){
            v = to[e];
            if (inS[v] || ! w[e]) continue;
            GET (v);
        }
    }
} G;

inline void ARKNIGHTS (){
    io::read (n), io::read (m);
    for (int i = 1;i <= n;++ i) for (int j = 1;j <= m;++ j){
        a[i][j] = io::next_blank ();
        if ((i ^ j) & 1){
            if (a[i][j] == 'B') a[i][j] = 'W';
            else
            if (a[i][j] == 'W') a[i][j] = 'B';
        }
    }
    G.s = vx (n, m, 2) + 1, G.t = G.lrg = G.s + 1;
    G.init ();
    for (int i = 1;i <= n;++ i) for (int j = 1;j <= m;++ j){
        if (a[i][j] == 'B') G.Add (G.s, vx (i, j, 0), inf);
        if (a[i][j] == 'W') G.Add (vx (i, j, 0), G.t, inf);
        if (i < n && j < m){
            G.Add (vx (i + 1, j + 1, 0), vx (i, j, 1), inf);
            G.Add (vx (i, j + 1, 0), vx (i, j, 1), inf);
            G.Add (vx (i + 1, j, 0), vx (i, j, 1), inf);
            G.Add (vx (i, j, 1), vx (i, j, 0), 1);

            G.Add (vx (i, j, 2), vx (i + 1, j + 1, 0), inf);
            G.Add (vx (i, j, 2), vx (i, j + 1, 0), inf);
            G.Add (vx (i, j, 2), vx (i + 1, j, 0), inf);
            G.Add (vx (i, j, 0), vx (i, j, 2), 1);
        }
    }
    io::write ((n - 1) * (m - 1) - G.FLOW ()), putchar ('\n'); G.GET (G.s);
    for (int i = 1;i <= n;++ i) for (int j = 1;j <= m;++ j){
        if (G.inS[vx (i, j, 0)]) a[i][j] = 'B';
        else a[i][j] = 'W';
        if ((i ^ j) & 1){
            if (a[i][j] == 'B') a[i][j] = 'W';
            else
            if (a[i][j] == 'W') a[i][j] = 'B';
        }
    }
    for (int i = 1;i <= n;++ i, putchar ('\n'))
        for (int j = 1;j <= m;++ j) putchar (a[i][j]);
}

signed main (){
    STCLOCK

    for (int T = io::read ();T --;ARKNIGHTS ());

    TIMENOW
    return 0;
}