#include <bits/stdc++.h>
using namespace std;
const int M = 1200000;
const int inf = 0x3f3f3f3f;
int n, m, k;
vector<int> g[M];
int ans;
int dfs(int u, int f) {
  vector<int> v = {0, 0};
  for (int to : g[u]) {
    if (to == f) continue;
    v.push_back(dfs(to, u));
  }
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  int sz = g[u].size();
  ans = max(ans, v[0] + v[1] + sz + 1);
  return v[0] + sz - 1;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t;
  cin >> t;
  for (int _ = (1); _ <= (t); ++_) {
    cin >> n;
    int u, v;
    for (int i = (1); i <= (n); ++i) g[i].clear();
    for (int i = (2); i <= (n); ++i) {
      cin >> u >> v;
      g[u].push_back(v);
      g[v].push_back(u);
    }
    ans = 0;
    dfs(1, 1);
    cout << ans << endl;
  }
  return 0;
}
