#include <cstdio>
#include <algorithm>
#include <cstring>
#include <iostream>
#include <map>
#include <set>
#include <vector>
#define pii pair <int, int>
#define xx first
#define yy second
#pragma comment(linker, "/STACK:102400000,102400000")
#define LL long long
using namespace std;

const int N = 101000, K = 110, INF = 1e9;

vector <int> g[N];
int d[N], a[N];

pii dfs (int u, int fa, int c) {
//    int flag = 0;
    if (a[u]) return pii (max (0, a[u]), min (INF, a[u]));
    pii res = pii (0, 1e9);
    for (int i = 0; i < g[u].size(); i++) {
        int v = g[u][i];
        if (v == fa) continue;
        pii tmp = dfs (v, u, c);
        if (tmp.xx == -1) return pii (-1, 0);
        res.xx = max (res.xx, tmp.xx - c);
        res.yy = min (res.yy, tmp.yy + c);
//        res.xx = max (res.xx, tmp.xx);
//        if (tmp)
//        flag = 1;
    }
//    if (!flag) return res;
    if (res.xx > res.yy) return pii (-1, 0);
//    cout << u << ' '<< res.xx << ' ' << res.yy << endl;
    return res;
}

int main () {
//    freopen ("in.txt", "r", stdin);
    int T;
    cin >>T;
    while (T--) {
        int n, k, u, v;
        cin >> n >> k;
        for (int i = 1; i <= n; i++) {
            d[i] = a[i] = 0;
            g[i].clear();
        }
        for (int i = 1; i < n; i++) {
            scanf ("%d%d", &u, &v);
            g[u].push_back (v);
            g[v].push_back (u);
            d[u]++;
            d[v]++;
        }
        for (int i = 1; i <= k; i++) {
            scanf ("%d%d", &u, &v);
            a[u] = v;
        }
        if (n == 2) {
            if (k == 1) cout << 0 << endl;
            else cout << abs (a[1] - a[2]) << endl;
            continue;
        }
        int rt = 0;
        for (int i = 1; i<= n; i++) if (d[i] != 1) { rt = i; break; }
//        cout << rt << endl;
        int l = -1, r = 1e9;
//        pii tmp = dfs (rt, 0, 1);
//        cout << tmp.xx << ' ' << tmp.yy << endl;
        while (l + 1 < r) {
            int m = (l + r) / 2;
            if (dfs (rt, 0, m).xx != -1) r = m;
            else l = m;
        }
        cout << r << endl;
    }
}