#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define ld long double
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pdd pair<ld, ld>
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second

const int NMAX = 100005;

int t, n;
int d[NMAX], dad[NMAX];
vector<int> v[NMAX];
pii e[NMAX];

void dfs(int x, int f) {
    for (auto it : v[x]) {
        if (it != f) {
            d[it] = d[x] + 1;
            dad[it] = x;
            dfs(it, x);
        }
    }
}

int calc(int x, int y) {
    int maxi, node, node2;

    for (auto &it : v[x])
        if (it == y) {
            swap(v[x].back(), it);
            v[x].pop_back();
            break;
        }

    for (auto &it : v[y])
        if (it == x) {
            swap(v[y].back(), it);
            v[y].pop_back();
            break;
        }

    memset(d, 0, sizeof(d));
    dfs(x, -1);
    maxi = 0, node = x;
    for (int i = 0; i < n; i++)
        if (d[i] > maxi) {
            maxi = d[i];
            node = i;
        }

    memset(d, 0, sizeof(d));
    dfs(node, -1);
    maxi = 0;
    for (int i = 0; i < n; i++)
        if (d[i] > maxi) {
            maxi = d[i];
            node2 = i;
        }

    int mlc = maxi;

    memset(d, 0, sizeof(d));
    dfs(y, -1);
    maxi = 0, node = y;
    for (int i = 0; i < n; i++)
        if (d[i] > maxi) {
            maxi = d[i];
            node = i;
        }

    memset(d, 0, sizeof(d));
    dfs(node, -1);
    maxi = 0;
    for (int i = 0; i < n; i++)
        if (d[i] > maxi) {
            maxi = d[i];
            node2 = i;
        }

    v[x].pb(y);
    v[y].pb(x);

    return (1 + (mlc + 1) / 2 + (maxi + 1) / 2);
}

int main() {
    srand(time(0));
    cin.sync_with_stdio(false);

    freopen("revolta.in", "r", stdin);
    freopen("revolta.out", "w", stdout);

    cin >> t;
    for (; t; t--) {
        cin >> n;

        for (int i = 0; i < n; i++)
            v[i].clear();

        for (int i = 1; i < n; i++) {
            int x, y;
            cin >> x >> y;
            v[x].pb(y);
            v[y].pb(x);
            e[i] = {x, y};
        }

        int sol = 1 << 30;
        for (int i = 1; i <= 10; i++) {
            int mlc = rand() % (n - 1) + 1;
            sol = min(sol, calc(e[mlc].fi, e[mlc].se));
        }

        cout << sol << '\n';
    }

    return 0;
}