#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int, int> pii; typedef vector<pair<int, int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

vector<int> t_parent;
vi t_ord;

void tree_getorder(const vector<vi> &g, int root) {
    int n = g.size();
    t_parent.assign(n, -1);
    t_ord.clear();

    vector<int> stk; stk.push_back(root);
    while(!stk.empty()) {
        int i = stk.back(); stk.pop_back();
        t_ord.push_back(i);
        for(int j = (int)g[i].size() - 1; j >= 0; j --) {
            int c = g[i][j];
            if(t_parent[c] == -1 && c != root)
                stk.push_back(c);
            else
                t_parent[i] = c;
        }
    }
}

int main() {
    int T;
    scanf("%d", &T);
    for(int ii = 0; ii < T; ++ ii) {
        int n; int k;
        scanf("%d%d", &n, &k);
        vector<vector<int> > g(n);
        for(int i = 0; i < n - 1; ++ i) {
            int u, v;
            scanf("%d%d", &u, &v), -- u, -- v;
            g[u].push_back(v);
            g[v].push_back(u);
        }
        vector<int> val(n, -1);
        rep(i, k) {
            int u; int w;
            scanf("%d%d", &u, &w), -- u;
            val[u] = w;
        }
        tree_getorder(g, 0);
        vector<pii> intervals;
        int lo = 0, up = (int)1e9;
        while(up - lo > 0) {
            int mid = (lo + up) / 2;
            intervals.assign(n, pii(1, (int)1e9));
            rep(i, n) if(val[i] != -1)
                intervals[i] = mp(val[i], val[i]);
            bool ok = true;
            for(int ix = (int)t_ord.size() - 1; ix > 0; -- ix) {
                int i = t_ord[ix], p = t_parent[i];
                amax(intervals[p].first, intervals[i].first - mid);
                amin(intervals[p].second, intervals[i].second + mid);
                if(intervals[p].first > intervals[p].second) {
                    ok = false;
                    break;
                }
            }
            if(ok)
                up = mid;
            else
                lo = mid + 1;
        }
        printf("%d\n", up);
    }
    return 0;
}