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

constexpr int M = 120, E = 4010, S = 1, T = 2, inf = 1000000;

char c;
int t, n, m, mp[M][M], id[M][M], dep[M], x[M], y[M];
int to[E], nxt[E], val[E], head[M], cur[M], tot;

inline void add(int u, int v, int w) {
    to[tot] = v, val[tot] = w, nxt[tot] = head[u], head[u] = tot++;
}
inline void add1(int u, int v) { add(u, v, 1), add(v, u, 0); }
inline void add2(int u, int v) { add(u, v, inf), add(v, u, inf); }

inline bool bfs() {
    queue<int> q;
    memset(dep, -1, sizeof(dep)), dep[S] = 0, q.push(S);
    while (!q.empty()) {
        int p = q.front();
        q.pop();
        for (int i = head[p]; i; i = nxt[i])
            if (val[i] && dep[to[i]] == -1) dep[to[i]] = dep[p] + 1, q.push(to[i]);
    }
    return dep[T] != -1;
}
int dfs(int n, int fl) {
    if (n == T) return fl;
    int lf = fl;
    for (int &i = cur[n]; i; i = nxt[i])
        if (dep[to[i]] == dep[n] + 1 && val[i]) {
            int g = dfs(to[i], min(fl, val[i]));
            lf -= g, val[i] -= g, val[i ^ 1] += g;
            if (!lf) return fl;
        }
    return fl - lf;
}
inline int dinic() {
    int result = 0;
    while (bfs()) memcpy(cur, head, sizeof(head)), result += dfs(S, inf);
    return result;
}

inline void solve() {
    assert(scanf("%d%d", &n, &m));
    memset(head, 0, sizeof(head)), tot = id[0][0] = 2;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++) {
            assert(scanf(" %c", &c));
            if (c == '?') mp[i][j] = -1;
            else mp[i][j] = ((i + j) & 1) ^ (c == 'W');
        }
    int ans = 0;
    for (int i = 1; i < n; i++)
        for (int j = 1; j < m; j++) id[i][j] = ++id[0][0], x[id[0][0]] = i, y[id[0][0]] = j;
    for (int i = 1; i < n; i++)
        for (int j = 1; j < m; j++) {
            bool e0 = false, e1 = false;
            for (int u = i; u <= i + 1; u++)
                for (int v = j; v <= j + 1; v++)
                    if (mp[u][v] == 1) e1 = true;
                    else if (mp[u][v] == 0) e0 = true;
            if (!e1) add1(S, id[i][j]), ans++;
            if (!e0) add1(id[i][j], T), ans++;
        }
    for (int i = 1; i < n; i++)
        for (int j = 1; j < m; j++) {
            if (i + 1 < n) add2(id[i][j], id[i + 1][j]);
            if (j + 1 < m) add2(id[i][j], id[i][j + 1]);
            if (i + 1 < n && j + 1 < m) add2(id[i][j], id[i + 1][j + 1]);
            if (i + 1 < n && j - 1 >= 1) add2(id[i][j], id[i + 1][j - 1]);
        }
    printf("%d\n", ans - dinic());
    bfs();
    for (int i = 1; i < n; i++)
        for (int j = 1; j < m; j++) {
            int t = dep[id[i][j]] != -1 ? 0 : 1;
            for (int u = i; u <= i + 1; u++)
                for (int v = j; v <= j + 1; v++)
                    if (mp[u][v] == -1) mp[u][v] = t;
        }
    for (int i = 1; i <= n; i++, printf("\n"))
        for (int j = 1; j <= m; j++) {
            // if (mp[i][j] == -1) mp[i][j] = 0;
            mp[i][j] ^= (i + j) & 1;
            putchar(mp[i][j] ? 'W' : 'B');
        }
}

int main() {
    assert(scanf("%d", &t));
    while (t--) solve();
    return 0;
}