#pragma comment(linker, "/STACK:102400000,102400000")
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
#define INF 0x3f3f3f3f
#define eps 1e-8
typedef long long LL;

int l[50010], r[50010], w[50010];
bool flag[50010];
vector<int> a[50010];
int t, n, k;

int Get_l(int x, int d)
{
    for (int i = 0; i < a[x].size(); i++)
    if (!flag[a[x][i]])
    {
        flag[a[x][i]] = 1;
        l[x] = max(l[x], Get_l(a[x][i], d));
    }
    return l[x] - d;
}

int Get_r(int x, int d)
{
    for (int i = 0; i < a[x].size(); i++)
    if (!flag[a[x][i]])
    {
        flag[a[x][i]] = 1;
        r[x] = min(r[x], Get_r(a[x][i], d));
    }
    return r[x] + d;
}

int Find()
{
    int ll = 0, rr = INF, mid;
    while (ll < rr)
    {
        mid = (ll+rr) >> 1;
        memset(l, 0, sizeof(l));
        memset(r, INF, sizeof(r));
        for (int i = 1; i <= n; i++)
            if (w[i]) l[i] = r[i] = w[i];
        memset(flag, 0, sizeof(flag));
        Get_l(1, mid);
        memset(flag, 0, sizeof(flag));
        Get_r(1, mid);
        bool p = 1;
        for (int i = 1; i <= n; i++)
        if (l[i] > r[i])
        {
            p = 0;
            break;
        }
        if (p) rr = mid;
        else ll = mid + 1;
    }
    return ll;
}

int main()
{
    scanf("%d", &t);
    while (t--)
    {
        scanf("%d%d", &n, &k);
        memset(w, 0, sizeof(w));
        memset(l, 0, sizeof(l));
        memset(r, INF, sizeof(r));
        for (int i = 1; i <= n; i++)
            a[i].clear();
        for (int i = 1, u, v; i < n; i++)
        {
            scanf("%d%d", &u, &v);
            a[u].push_back(v);
            a[v].push_back(u);
        }
        for (int i = 0, uu, ww; i < k; i++)
        {
            scanf("%d%d", &uu, &ww);
            w[uu] = ww;
        }
        printf("%d\n", Find());
    }
    return 0;
}