public static void main(String[] args) {
    Scanner sc = new Scanner();
    int t = sc.nextInt();
    for (int currentCase = 0; currentCase < t; currentCase++) {
      int r = sc.nextInt();
      sc.nextInt();
      char[][] board = sc.nextGrid(r);
      int[][] left = new int[board.length][board[0].length];
      for (int i = 0; i < board.length; i++) {
        int start = 0;
        for (int j = 0; j < board[0].length; j++) {
          if (board[i][j] != '#') {
            start = 0;
            left[i][j] = 0;
          } else {
            left[i][j] = start;
            start++;
          }
        }
      }
      int[][] right = new int[board.length][board[0].length];
      int[][] center = new int[board.length][board[0].length];
      for (int i = 0; i < board.length; i++) {
        int start = 0;
        for (int j = board[0].length - 1; j >= 0; j--) {
          if (board[i][j] != '#') {
            start = 0;
            right[i][j] = 0;
            center[i][j] = 0;
          } else {
            right[i][j] = start;
            start++;
            center[i][j] = 2 * Math.min(left[i][j], right[i][j]) + 1;
          }
        }
      }
      int[][] up = new int[board.length][board[0].length];
      for (int i = 0; i < board.length; i++) {
        int start = 0;
        for (int j = 0; j < board[0].length; j++) {
          if (board[i][j] == '#') {
            if (i == 0 || up[i - 1][j] == 0) {
              up[i][j] = 1;
            } else {
              up[i][j] = Math.min(center[i][j], up[i - 1][j] + 2);
            }
          } else {
            up[i][j] = 0;
          }
        }
      }
      int[][] down = new int[board.length][board[0].length];
      int best = 0;
      for (int i = board.length - 1; i >= 0; i--) {
        int start = 0;
        for (int j = 0; j < board[0].length; j++) {
          if (board[i][j] == '#') {
            if (i == board.length - 1 || down[i + 1][j] == 0) {
              down[i][j] = 1;
            } else {
              down[i][j] = Math.min(center[i][j], down[i + 1][j] + 2);
            }
            best = Math.max(best, Math.min(up[i][j], down[i][j]));
          } else {
            down[i][j] = 0;
          }
        }
      }
      System.out.println(best);
  }
}