#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;

inline int rd() {
    int x = 0;
    bool f = 0;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) f |= (c == '-');
    for (; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);
    return f ? -x : x;
}

#define eb emplace_back
#define all(s) (s).begin(), (s).end()
#define rep(i, a, b) for (int i = (a); i <= (b); ++i)
#define per(i, a, b) for (int i = (a); i >= (b); --i)

template<typename T>
void getmin(T &a, T b) {a = (a > b ? b : a);}

template <const int V, const int inf = 1000000000>
struct Hopcroft_Karp {
    bool vis[V];
    vector<int> e[V];
    int nl, nr, ml[V], mr[V], dl[V], dr[V];
    inline void reset(int _nl, int _nr) {
        nl = _nl; rep(i, 0, nl) ml[i] = 0, e[i].clear();
        nr = _nr; rep(i, 0, nr) mr[i] = 0, vis[i] = false;
    }
    inline bool bfs() {
        static int q[V], hd, tl, dT; hd=1; tl=0; dT=inf;
        memset(dl,-1,sizeof(int) * (nl + 1));
        memset(dr,-1,sizeof(int) * (nr + 1));
        for (int i=1; i<=nl; ++i) if (!ml[i]) {dl[i] = 0; q[++tl] = i;}
        for (int u;hd<=tl;) {
            if(dl[u=q[hd++]]>=dT) break;
            for (auto v:e[u])
                if (dr[v] == -1) {
                    dr[v] = dl[u] + 1;
                    if(!mr[v]) getmin(dT, dr[v] + 1);
                    else {dl[mr[v]] = dr[v] + 1; q[++tl] = mr[v];}
                }
        }
        return dT != inf;
    }
    bool dfs(int u) {
        for(auto v:e[u]) {
            if (vis[v]||dl[u]+1!=dr[v]) continue;
            vis[v]=true;
            if(!mr[v] || dfs(mr[v])) {
                mr[v]=u; ml[u]=v; return true;
            }
        }
        return false;
    }
    inline void add(int u,int v) {e[u].push_back(v);}
    inline int max_match() {
        int ans=0;
        while(bfs()) {
            memset(vis,0,sizeof(bool)*(nr+1));
            for(int i=1;i<=nl;++i) if(!ml[i]) ans+=dfs(i);
        }
        return ans;
    }
};

Hopcroft_Karp<250000> G;

const int N = 507;

char s[N][N];

int id[N][N];

inline void work() {
    int n = rd(), m = rd();
    int cntW = 0, cntB = 0;
    rep(i, 1, n) rep(j, 1, m) {
        char c = getchar();
        while (c != '.' && !isalpha(c)) c = getchar();
        s[i][j] = c;
        if (c == 'B') id[i][j] = ++cntB;
        if (c == 'W') id[i][j] = ++cntW;
    }
    if (cntW != cntB * 2) {puts("NO"); return;}
    G.reset(cntW, cntW);
    rep(i, 1, n) rep(j, 1, m)
        if (s[i][j] == 'B') {
            int ud = (id[i][j] << 1);
            if (s[i - 1][j] == 'W') G.add(ud, id[i - 1][j]);
            if (s[i + 1][j] == 'W') G.add(ud, id[i + 1][j]);
            int lr = ud - 1;
            if (s[i][j - 1] == 'W') G.add(lr, id[i][j - 1]);
            if (s[i][j + 1] == 'W') G.add(lr, id[i][j + 1]);
        }
    puts(G.max_match() == cntW ? "YES" : "NO");
}

int main() {
    per(t, rd(), 1) work();
    return 0;
}