#include <fstream>
#include <vector>
#include <algorithm>
#include <queue>
#include <deque>
using namespace std;
ifstream fin("zvon.in");
ofstream fout("zvon.out");
int n, t, tc, x, y, i, mx, tm;
vector <int> d, gr, orx, sr;
vector <vector<int>> v, bkv;
bool comp (int a, int b)
{
    return d[a] > d[b];
}
void dfs(int k)
{
    sr[k] = 1;
    gr[k] = ++tm;
    for (int i = 0; i < v[k].size(); i++)
    {
        if (sr[v[k][i]] == 0)
            dfs(v[k][i]);
    }
    orx[k] = ++tm;
    d[k] = (orx[k]-gr[k]+1)/2;
}
int main()
{
    fin >> t;
    for (tc = 1; tc <= t; tc++)
    {
        fin >> n; v.resize(n+1); bkv.resize(n+1); gr.resize(n+1); orx.resize(n+1); sr.resize(n+1); tm = 0;
        for (i = 1; i < n; i++)
        {
            fin >> x >> y;
            v[x].push_back(y);
            bkv[y].push_back(x);
        }
        d.resize(n+1);
        dfs(1);
        for (i = 1; i <= n; i++)
        {
            sort (v[i].begin(), v[i].end(), comp);
        }
        queue <int> q;
        q.push(1);
        vector <int> s;
        s.resize(n+1);
        s[1] = 1;
        mx = 0;
        while (!q.empty())
        {
            y = q.front();
            q.pop();
            for (x = 0; x < v[y].size(); x++)
            {
                if (s[v[y][x]] == 0)
                    s[v[y][x]] = s[y]+x+1, q.push(v[y][x]), mx = max(mx, s[v[y][x]]);
            }
        }
        if (mx > 0)
            fout << mx-1 << "\n";
        else fout << "0\n";
        v.resize(1);
        bkv.resize(1);
        d.resize(1); gr.resize(1); orx.resize(1); sr.resize(1);
    }
    return 0;
}