#include<bits/stdc++.h>
#define LL long long
using namespace std;
int T,n,m,s;
string Mp[1005];
string vis[1005];
bool check(int x,int y){
	return 1<=x&&x<=n&&1<=y&&y<=m&&Mp[x][y-1]=='W'&&vis[x][y-1]=='0';
}
bool bfs(){
	if(Mp[1][0]=='B'||Mp[n][m-1]=='B') return 0;
	queue<pair<int ,int> > q;
	q.push({1,1});
	vis[1][0]='1';
	while(q.size()){
		int hx=q.front().first,hy=q.front().second;
		q.pop();
		if(check(hx+1,hy)){
			q.push({hx+1,hy});
			vis[hx+1][hy-1]='1';
		}
		if(check(hx,hy+1)){
			q.push({hx,hy+1});
			vis[hx][hy]='1';
		}
		if(check(hx-1,hy)){
			q.push({hx-1,hy});
			vis[hx-1][hy-1]='1';
		}
		if(check(hx,hy-1)){
			q.push({hx,hy-1});
			vis[hx][hy-2]='1';
		}
	}
	return vis[n][m-1]=='1';
}
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	cin>>T;
	while(T--){
		cin>>n>>m;
		s=n*m;
		s-=n+m-1;
		for(int i=1;i<=n;++i){
			cin>>Mp[i];
			vis[i].clear();
			for(int j=0;j<m;++j){
				if(Mp[i][j]=='B') s--;
				vis[i].push_back('0');
			}
		}
		if(!bfs()){
			cout<<'J';
			continue;
		}
		if(s&1) cout<<'I';
		else cout<<'J';
		cout<<'\n';
	}
	return 0;
}