#include<iostream>
#include<set>
#include<queue>
#include<map>
#include<cmath>
#include<string>
#include<vector>
#include<cstring>
#include<algorithm>
#include<unordered_map>

#define pb push_back
#define fi first
#define se second
#define int long long
#define all(x) (x).begin(),(x).end()
#define _for(i, a) for(int i = 0; i < (a); ++i) 
#define _rep(i, a, b) for(int i = (a);i <= (b); ++i)
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define u1 (u<<1)
#define u2 (u<<1|1)
//#define endl '\n'
using namespace std;
typedef pair<int,int> PII;

const int INF=0x3f3f3f3f;
const int P=1e9+7;
const int N=1020,M=2*N;
int n,m,k,q[N];
char g[N][N];
int dist[N][N];
int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};
void bfs()
{
	memset(dist,0x3f,sizeof(dist));
	queue<PII>q;
	q.push({1,1});
	dist[1][1]=1;
	while(q.size())
	{
		auto t=q.front();
		q.pop();
		int xx=t.first,yy=t.second;
		_rep(i,0,3)
		{
			int x=xx+dx[i],y=yy+dy[i];
			if(x<1||y<1||x>n||y>m)continue;
			if(dist[x][y]>dist[xx][yy]+1&&g[x][y]=='W')
			{
				dist[x][y]=dist[xx][yy]+1;
				q.push({x,y});
			}
		}
	}
	return ;
}
void solve(){
	cin>>n>>m;
	int cnt=0;
	_rep(i,1,n)
		_rep(j,1,m)
		{
			cin>>g[i][j];
			if(g[i][j]=='B')cnt++;	
		}
	bfs();
	if(dist[n][m]<0x3f3f3f3f/2&&g[1][1]=='W'&&g[n][m]=='W')
	{
		int now=n*m-cnt-dist[n][m];
		if(now%2)cout<<"I\n";
		else cout<<"J\n";
	}
	else cout<<"J\n";
}
signed main(){
	IOS;
	int T=1;
	cin>>T;
	_rep(i,1,T){
		solve();
	}
	return 0;
}