1 #include <cstdio>
 2 #include <cstring>
 3 #include <iostream>
 4 #include <algorithm>
 5 #include <cmath>
 6 #include <string>
 7 #include <vector>
 8 #include <queue>
 9 #include <set>
10 using namespace std;
11
12 #define ll long long
13 #define inf 0x3f3f3f3f
14 #define eps 1e-8
15 #define maxn 180000
16 #define maxm 360000
17
18 int vv[maxm],nxt[maxm];
19 int head[maxn],E;
20 void init(){memset(head,-1,sizeof(head));E=0;}
21 void addedge(int u,int v){
22     vv[E]=v,nxt[E]=head[u],head[u]=E++;
23 }
24 int pre[maxn];
25 int vis[maxn];
26 bool match(int x,int n,int ID){
27     for(int i=head[x];i!=-1;i=nxt[i]){
28         int v = vv[i]-n;
29         if(vis[v]==ID)continue;
30         vis[v] = ID;
31         if(pre[v]==-1 || match(pre[v],n,ID)){
32             pre[v]=x;
33             return true;
34         }
35     }
36     return false;
37 }
38 bool hungary(int n){
39     memset(pre,-1,sizeof(pre));
40     memset(vis,0,sizeof(vis));
41     for(int i=1;i<=n;++i)
42         if(match(i,n,i)==false)return false;
43     return true;
44 }
45
46 char ch[555][555];
47 int idx[555][555];
48 int bx[maxn],by[maxn];
49 int main(){
50     int t;
51     scanf("%d",&t);
52     while(t--){
53         int nn,mm;
54         scanf("%d%d",&nn,&mm);
55         memset(ch,0,sizeof(ch));
56         for(int i=1;i<=nn;++i)scanf("%s",ch[i]+1);
57         int B=0,W=0;
58         for(int i=1;i<=nn;++i)for(int j=1;j<=mm;++j)
59             if(ch[i][j]=='B')idx[i][j]=++B,bx[B]=i,by[B]=j;
60             else if(ch[i][j]=='W')idx[i][j]=++W;
61         if(B*2!=W){puts("NO");continue;}
62         init();
63         for(int b=1;b<=B;++b){
64             int i=bx[b],j=by[b];
65             if(ch[i-1][j]=='W')addedge(idx[i][j],B*2+idx[i-1][j]);
66             if(ch[i+1][j]=='W')addedge(idx[i][j],B*2+idx[i+1][j]);
67             if(ch[i][j-1]=='W')addedge(idx[i][j]+B,B*2+idx[i][j-1]);
68             if(ch[i][j+1]=='W')addedge(idx[i][j]+B,B*2+idx[i][j+1]);
69         }
70         if(hungary(B<<1))puts("YES");
71         else puts("NO");
72     }
73     return 0;
74 }