#include<bits/stdc++.h>
using namespace std;
using ll = long long;
template< typename flow_t >
struct Dinic {
    const flow_t INF;

    struct edge {
        int to;
        flow_t cap;
        int rev;
        bool isrev;
        int idx;
    };

    vector< vector< edge > > graph;
    vector< int > min_cost, iter;

    Dinic(int V) : INF(numeric_limits< flow_t >::max()), graph(V) {}

    void add_edge(int from, int to, flow_t cap, int idx = -1) {
        graph[from].emplace_back((edge) {to, cap, (int) graph[to].size(), false, idx});
        graph[to].emplace_back((edge) {from, 0, (int) graph[from].size() - 1, true, idx});
    }

    bool bfs(int s, int t) {
        min_cost.assign(graph.size(), -1);
        queue< int > que;
        min_cost[s] = 0;
        que.push(s);
        while(!que.empty() && min_cost[t] == -1) {
            int p = que.front();
            que.pop();
            for(auto &e : graph[p]) {
                if(e.cap > 0 && min_cost[e.to] == -1) {
                    min_cost[e.to] = min_cost[p] + 1;
                    que.push(e.to);
                }
            }
        }
        return min_cost[t] != -1;
    }

    flow_t dfs(int idx, const int t, flow_t flow) {
        if(idx == t) return flow;
        for(int &i = iter[idx]; i < graph[idx].size(); i++) {
            edge &e = graph[idx][i];
            if(e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
                flow_t d = dfs(e.to, t, min(flow, e.cap));
                if(d > 0) {
                    e.cap -= d;
                    graph[e.to][e.rev].cap += d;
                    return d;
                }
            }
        }
        return 0;
    }

    flow_t max_flow(int s, int t) {
        flow_t flow = 0;
        while(bfs(s, t)) {
            iter.assign(graph.size(), 0);
            flow_t f = 0;
            while((f = dfs(s, t, INF)) > 0) flow += f;
        }
        return flow;
    }

    void output() {
        for(int i = 0; i < graph.size(); i++) {
            for(auto &e : graph[i]) {
                if(e.isrev) continue;
                auto &rev_e = graph[e.to][e.rev];
                cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << e.cap + rev_e.cap << ")" << endl;
            }
        }
    }
};

void solve(){
    int n,m;
    cin>>n>>m;
    int h = n;int w = m;
    Dinic<int> dinic(2*n*m+2);
    int st = 2 * n * m;
    int t = st + 1;
    int a = 0;
    int b = 0;
    int dx[] = {1,-1,0,0};
    int dy[] = {0,0,1,-1};
    vector<string> s(n);
    for(int i = 0;i<n;i++) cin>>s[i];
    for(int i = 0;i<n;i++){
        for(int j = 0;j<m;j++){
            if(s[i][j]=='.') continue;
            int ni = i * w + j;
            if(s[i][j]=='W'){
                a++;
                dinic.add_edge(ni,t,1);
                continue;
            }
            b++;
            dinic.add_edge(st,ni,1);
            dinic.add_edge(st,ni+n*m,1);
            for(int k = 0;k<4;k++){
                int nni = i + dx[k];
                int nnj = j + dy[k];
                if(nni<0||nni>=n||nnj<0||nnj>=m) continue;
                if(s[nni][nnj]!='W') continue;
                if(k<2) dinic.add_edge(ni,nni*w+nnj,1);
                else dinic.add_edge(ni+n*m,nni*w+nnj,1);
            }
        }
    }
    int can = dinic.max_flow(st,t);
    if(a==2*b&&can==a) cout<<"YES\n";
    else cout<<"NO\n";
                

}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t;
    cin>>t;
    while(t--){
        solve();
    }
}