#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif
const int MAX_N = 1010;
int grid[MAX_N][MAX_N];
int dp[MAX_N][MAX_N], pf[MAX_N][MAX_N], up[MAX_N];
int solve() {
  int n, m;
  cin >> n >> m;
  for (int i = 1;i <= n;++i) {
    for (int j = 1;j <= m;++j)
      cin >> grid[i][j];
  }
  int res = 1;
  for (int i = 1;i <= n;++i) for (int j = 1;j <= m;++j) {
    pf[i][j] = pf[i-1][j] + pf[i][j-1] - pf[i-1][j-1] + (grid[i][j] == 1);
    if (grid[i][j] == 1) {
      dp[i][j] = 0;
      continue;
    }
    if (dp[i][j-1] == dp[i-1][j]) {
      int d = dp[i][j-1];
      if (d == 0) dp[i][j] = 1;
      else {
        if (grid[i - d][j - d] == 0)
          dp[i][j] = d + 1;
        else
          dp[i][j] = d;
      }
    } else dp[i][j] = min(dp[i][j-1], dp[i-1][j]) + 1;
    chmax(res, dp[i][j]);
  }
  for (int i = 1;i <= n;++i) up[i] = 0;

  for (int i = 1;i <= n;++i) {
    int f = 0;
    for (int j = 1;j <= m;++j) {
      int a = 0;
      auto valid = [&](int a) {
        return pf[i][j] - pf[i-a][j] - pf[i][j-a] + pf[i-a][j-a] <= 1;
      };
      if (grid[i][j] == 1) {
        if (dp[i-1][j] == dp[i][j-1]) {
          a = dp[i-1][j];
          if (grid[i-a][j-a] == 0 || a == 0) ++a;
        } else {
          a = min(dp[i-1][j], dp[i][j-1]) + 1;
        }
        f = j;
        up[j] = i;
      } else {
        vector<int> v{dp[i-1][j-1] + 2, j - f+1, i - up[j]+1};
        sort(AI(v));
        if (v[0] == v[1]) {
          a = v[0] - 1;
        } else a = v[1] - 1;
      }
      if (!valid(a)) --a;
      chmax(res, a);
    }
  }
  return res;
}
int32_t main() {
    ios_base::sync_with_stdio(0), cin.tie(0);
  int T;
  cin >> T;
  while (T--)
    cout << solve() << '\n';
}