#include <bits/stdc++.h>
template <class Tp>
using vc = std::vector<Tp>;
template <class Tp>
using vvc = std::vector<std::vector<Tp>>;
struct CustomHash {
  static constexpr uint64_t splitmix64(uint64_t x) {
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  static constexpr size_t append(size_t x, size_t y) {
    return x ^ (y >> 1) ^ ((y & 1) << (sizeof(size_t) * 8 - 1));
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
      std::chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
  template <class Tp, class Up>
  size_t operator()(std::pair<Tp, Up> const &p) const {
    return append((*this)(p.first), (*this)(p.second));
  }
  template <typename... Ts>
  size_t operator()(std::tuple<Ts...> const &tp) const {
    size_t ret = 0;
    std::apply(
      [&](Ts const &...targs) { ((ret = append(ret, (*this)(targs))), ...); },
      tp);
    return ret;
  }
  template <
    class Tp,
    std::enable_if_t<std::is_same<decltype(std::declval<Tp>().begin()),
                                  typename Tp::iterator>::value &&
                     std::is_same<decltype(std::declval<Tp>().end()),
                                  typename Tp::iterator>::value> * = nullptr>
  size_t operator()(Tp const &tp) const {
    size_t ret = 0;
    for (auto &&i : tp) ret = append(ret, (*this)(i));
    return ret;
  }
};
using u32 = uint32_t;
template <class Tp>
constexpr auto chkmin(Tp &a, Tp b) -> bool {
  return b < a ? a = b, true : false;
}
template <class Tp>
constexpr auto chkmax(Tp &a, Tp b) -> bool {
  return a < b ? a = b, true : false;
}
template <class Tp>
constexpr auto ispow2(Tp i) -> bool {
  return i && (i & -i) == i;
}
#define TPL_SIZE_(Tuple) std::tuple_size_v<std::remove_reference_t<Tuple>>
namespace tuple_detail_ {
template <std::size_t Begin, class Tuple, std::size_t... Is>
constexpr auto subtuple_impl_(Tuple &&t, std::index_sequence<Is...>) {
  return std::make_tuple(std::get<Is + Begin>(t)...);
}
template <class Tuple, class BinOp, std::size_t... Is>
constexpr auto
apply2_impl_(BinOp &&f, Tuple &&lhs, Tuple &&rhs, std::index_sequence<Is...>) {
  return std::make_tuple(
    std::forward<BinOp>(f)(std::get<Is>(lhs), std::get<Is>(rhs))...);
}
}  // namespace tuple_detail_
template <std::size_t Begin, std::size_t Len, class Tuple>
constexpr auto subtuple(Tuple &&t) {
  static_assert(Begin <= TPL_SIZE_(Tuple) && Len <= TPL_SIZE_(Tuple) &&
                  Begin + Len <= TPL_SIZE_(Tuple),
                "Out of range");
  return tuple_detail_::subtuple_impl_<Begin>(t,
                                              std::make_index_sequence<Len>());
}
template <std::size_t Pos, class Tp, class Tuple>
constexpr auto tuple_push(Tp &&v, Tuple &&t) {
  static_assert(TPL_SIZE_(Tuple) > 0, "Pop from empty tuple");
  return std::tuple_cat(subtuple<0, Pos>(t),
                        std::make_tuple(v),
                        subtuple<Pos, TPL_SIZE_(Tuple) - Pos>(t));
}
template <class Tp, class Tuple>
constexpr auto tuple_push_front(Tp &&v, Tuple &&t) {
  return tuple_push<0>(v, t);
}
template <class Tp, class Tuple>
constexpr auto tuple_push_back(Tp &&v, Tuple &&t) {
  return tuple_push<TPL_SIZE_(Tuple)>(v, t);
}
template <std::size_t Pos, class Tuple>
constexpr auto tuple_pop(Tuple &&t) {
  static_assert(TPL_SIZE_(Tuple) > 0, "Pop from empty tuple");
  return std::tuple_cat(subtuple<0, Pos>(t),
                        subtuple<Pos + 1, TPL_SIZE_(Tuple) - Pos - 1>(t));
}
template <class Tuple>
constexpr auto tuple_pop_front(Tuple &&t) {
  return tuple_pop<0>(t);
}
template <class Tuple>
constexpr auto tuple_pop_back(Tuple &&t) {
  return tuple_pop<TPL_SIZE_(Tuple) - 1>(t);
}
template <class Tuple, class BinOp>
constexpr auto apply2(BinOp &&f, Tuple &&lhs, Tuple &&rhs) {
  return tuple_detail_::apply2_impl_(
    f, lhs, rhs, std::make_index_sequence<TPL_SIZE_(Tuple)>());
}
#define OO_PTEQ_(op)                                                          \
  template <class Tp, class Up>                                               \
  constexpr auto operator op(std::pair<Tp, Up> lhs,                           \
                             const std::pair<Tp, Up> &rhs) {                  \
    return std::pair<Tp, Up>{lhs.first op rhs.first,                          \
                             lhs.second op rhs.second};                       \
  }                                                                           \
  template <class... Ts>                                                      \
  constexpr auto operator op(std::tuple<Ts...> const &lhs,                    \
                             std::tuple<Ts...> const &rhs) {                  \
    return apply2([](auto &&l, auto &&r) { return l op r; }, lhs, rhs);       \
  }                                                                           \
  template <class Tp, class Up>                                               \
  constexpr std::pair<Tp, Up> &operator op##=(std::pair<Tp, Up> &lhs,         \
                                              const std::pair<Tp, Up> &rhs) { \
    lhs.first op## = rhs.first;                                               \
    lhs.second op## = rhs.second;                                             \
    return lhs;                                                               \
  }                                                                           \
  template <class... Ts>                                                      \
  constexpr auto operator op##=(std::tuple<Ts...> &lhs,                       \
                                const std::tuple<Ts...> &rhs) {               \
    return lhs = lhs op rhs;                                                  \
  }
OO_PTEQ_(+)
OO_PTEQ_(-)
OO_PTEQ_(*)
OO_PTEQ_(/)
OO_PTEQ_(%)
OO_PTEQ_(&)
OO_PTEQ_(|)
OO_PTEQ_(^)
OO_PTEQ_(<<)
OO_PTEQ_(>>)
#undef OO_PTEQ_
#undef TPL_SIZE_
template <class Tp, class Up>
std::istream &operator>>(std::istream &is, std::pair<Tp, Up> &p) {
  return is >> p.first >> p.second;
}
template <class Tp, class Up>
std::ostream &operator<<(std::ostream &os, const std::pair<Tp, Up> &p) {
  return os << p.first << ' ' << p.second;
}
template <typename... Ts>
std::istream &operator>>(std::istream &is, std::tuple<Ts...> &p) {
  std::apply([&](Ts &...targs) { ((is >> targs), ...); }, p);
  return is;
}
template <typename... Ts>
std::ostream &operator<<(std::ostream &os, const std::tuple<Ts...> &p) {
  std::apply(
    [&](Ts const &...targs) {
      std::size_t n{0};
      ((os << targs << (++n != sizeof...(Ts) ? " " : "")), ...);
    },
    p);
  return os;
}
template <
  class Ch,
  class Tr,
  class Ct,
  std::enable_if_t<std::is_same<decltype(std::declval<Ct>().begin()),
                                typename Ct::iterator>::value &&
                   std::is_same<decltype(std::declval<Ct>().end()),
                                typename Ct::iterator>::value> * = nullptr>
std::basic_ostream<Ch, Tr> &operator<<(std::basic_ostream<Ch, Tr> &os,
                                       const Ct &x) {
  if (x.begin() == x.end()) return os;
  for (auto it = x.begin(); it != x.end() - 1; ++it) os << *it << ' ';
  os << x.back();
  return os;
}
const u32 K = 21;
using namespace std;
template <typename data_t,
          typename query_func =
            std::function<data_t(const data_t &, const data_t &)>>
class RMQ_ST_2D {
protected:
  query_func qfunc;
  std::vector<std::vector<std::vector<data_t>>> f;

public:
  RMQ_ST_2D() = delete;
  RMQ_ST_2D(query_func qfunc): qfunc(qfunc), f() {}
  template <typename init_func = std::function<data_t(size_t, size_t)>>
  void init(size_t n, size_t m, init_func ifunc) {
    const size_t K = (size_t)std::log2(std::max(n, m)) + 1;
    f.resize(K);
    for (auto &i : f) {
      i.resize(n);
      for (auto &j : i) j.resize(m);
    }
    for (size_t i = 0; i < n; ++i)
      for (size_t j = 0; j < m; ++j) f[0][i][j] = ifunc(i, j);
    for (size_t k = 1, p = 1, q = 2; k < K; ++k, p = q, q *= 2)
      for (int i = 0; i + q - 1 < n; ++i)
        for (int j = 0; j + q - 1 < m; ++j)
          f[k][i][j] = qfunc(qfunc(f[k - 1][i][j], f[k - 1][i + p][j]),
                             qfunc(f[k - 1][i][j + p], f[k - 1][i + p][j + p]));
  }
  data_t query(size_t x, size_t y, size_t l) const {
    size_t _ = (size_t)std::log2(l);
    return qfunc(qfunc(f[_][x][y], f[_][x + l - (1 << _)][y]),
                 qfunc(f[_][x][y + l - (1 << _)],
                       f[_][x + l - (1 << _)][y + l - (1 << _)]));
  }
};
auto solve([[maybe_unused]] int t_ = 0) -> void {
  int n, m;
  cin >> n >> m;
  vvc<int> a(n, vc<int>(m));
  for (auto &i : a)
    for (auto &j : i) cin >> j;
  RMQ_ST_2D<int> st([](int x, int y) { return min(x, y); });
  st.init(n, m, [&](size_t x, size_t y) { return a[x][y]; });
  auto check = [&](int g) {
    int mx = 0;
    for (int i = 0; i <= n - g; ++i)
      for (int j = 0; j <= m - g; ++j) mx = max(mx, st.query(i, j, g));
    return mx >= g;
  };
  int l = 1, r = min(n, m), ans = l;
  while (l <= r) {
    auto m = r - (r - l) / 2;
    if (check(m)) l = (ans = m) + 1;
    else r = m - 1;
  }
  cout << ans << '\n';
}
int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int i_ = 0;
  int t_ = 0;
  std::cin >> t_;
  for (i_ = 0; i_ < t_; ++i_) solve(i_);
  return 0;
}