#include <bits/stdc++.h>
using namespace std;
template <typename T>
void maxtt(T& t1, T t2) {
  t1 = max(t1, t2);
}
template <typename T>
void mintt(T& t1, T t2) {
  t1 = min(t1, t2);
}
bool debug = 0;
int n, m, k;
string direc = "URDL";
const long long MOD2 = (long long)998244353 * (long long)998244353;
long long ln, lk, lm;
void etp(bool f = 0) {
  puts(f ? "YES" : "NO");
  exit(0);
}
void addmod(int& x, int y, int mod = 998244353) {
  x += y;
  if (x >= mod) x -= mod;
  if (x < 0) x += mod;
  assert(x >= 0 && x < mod);
}
void et(int x = -1) {
  printf("%d\n", x);
  exit(0);
}
long long fastPow(long long x, long long y, int mod = 998244353) {
  long long ans = 1;
  while (y > 0) {
    if (y & 1) ans = (x * ans) % mod;
    x = x * x % mod;
    y >>= 1;
  }
  return ans;
}
long long gcd1(long long x, long long y) { return y ? gcd1(y, x % y) : x; }
vector<int> mp[300135];
bool lf[300135];
int dp[300135], ans;
void dfs(int x, int pa) {
  if (lf[x]) {
    dp[x] = 1;
    return;
  }
  multiset<int> sp;
  dp[x] = 1;
  int cs = 0;
  for (int c : mp[x])
    if (c != pa) {
      cs++;
      dfs(c, x);
      sp.insert(dp[c]);
      if (sp.size() > 2) sp.erase(sp.begin());
    }
  if (sp.size() == 1) {
    dp[x] = 1 + *sp.begin();
    maxtt(ans, dp[x]);
    return;
  }
  int A = *sp.begin(), B = *sp.rbegin();
  maxtt(ans, A + B + 1 + cs - 2 + (pa != 0));
  dp[x] = cs + B;
}
void fmain(int tid) {
  scanf("%d", &n);
  for (int(i) = 1; (i) <= (int)(n); (i)++) {
    mp[i].clear();
    lf[i] = 0;
    dp[i] = 0;
  }
  ans = 0;
  for (int i = 0, u, v; i < n - 1; i++) {
    scanf("%d%d", &u, &v);
    mp[u].push_back(v);
    mp[v].push_back(u);
  };
  if (n == 2) {
    puts("2");
    return;
  }
  int R;
  for (int(i) = 1; (i) <= (int)(n); (i)++) {
    if (mp[i].size() == 1)
      lf[i] = 1;
    else
      R = i;
  }
  dfs(R, 0);
  printf("%d\n", ans);
}
int main() {
  int t = 1;
  scanf("%d", &t);
  for (int(i) = 1; (i) <= (int)(t); (i)++) {
    fmain(i);
  }
  return 0;
}
