#include <bits/stdc++.h>
using namespace std;
constexpr int M = 220, E = 4010, S = 1, T = 2, inf = 1000000;
char c;
int t, n, m, e, 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 add(int u, int v) {
// printf("add %d -> %d\n", u, v);
add(u, v, 1), add(v, u, 0);
}
inline void adde(int u, int v) {
// printf("add %d -> %d\n", u, v);
add(u, v + e, inf), add(v + e, u, 0);
add(v, u + e, inf), add(u + e, v, 0);
}
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)), e = (n - 1) * (m - 1);
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;
add(id[i][j], id[i][j] + e, inf), add(id[i][j] + e, id[i][j], 0);
if (!e1) add(S, id[i][j]), ans++;
if (!e0) add(id[i][j] + e, T), ans++;
}
for (int i = 1; i < n; i++)
for (int j = 1; j < m; j++) {
if (i + 1 < n) adde(id[i][j], id[i + 1][j]);
if (j + 1 < m) adde(id[i][j], id[i][j + 1]);
if (i + 1 < n && j + 1 < m) adde(id[i][j], id[i + 1][j + 1]);
if (i + 1 < n && j - 1 >= 1) adde(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;
// printf("%d %d :: %d\n", i, j, t);
// 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 = head[S]; i; i = nxt[i])
if (val[i]) {
// printf("!!! %d %d\n", x[to[i]], y[to[i]]);
for (int u = x[to[i]]; u <= x[to[i]] + 1; u++)
for (int v = y[to[i]]; v <= y[to[i]] + 1; v++) assert(mp[u][v] == 0 || mp[i][j] == -1), mp[u][v] = 0;
}
for (int i = 1; i <= n; i++, printf("\n"))
for (int j = 1; j <= m; j++) {
if (mp[i][j] == -1) mp[i][j] = 1;
mp[i][j] ^= (i + j) & 1;
putchar(mp[i][j] ? 'W' : 'B');
}
}
int main() {
assert(scanf("%d", &t));
while (t--) solve();
return 0;
}